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000
FXUS66 KOTX 212256
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
256 PM PST SAT NOV 21 2009
.SYNOPSIS...
A STRONGER AND COLDER STORM SYSTEM WILL BRING THE POTENTIAL FOR
MODERATE TO HEAVY SNOWFALL OVER MUCH OF THE REGION TONIGHT AND
SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO PASS THROUGH
THE INLAND NORTHWEST EVERY 24 TO 36 HOURS THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...
...LIGHT TO MODERATE SNOWFALL EXPECTED TONIGHT THROUGH SUNDAY
ACROSS THE INLAND NW...
TONIGHT THROUGH SUNDAY...AFTERNOON WATER VAPOR SHOWING A STRONG
PACIFIC STORM CHARGING TOWARD THE WASHINGTON COAST WITH A CLASSIC
BAROCLINIC LEAF SIGNATURE INDICATIVE OF THE ORGANIZED DEEPENING
SURFACE CYCLONE AND ASSOCIATED CONVEYOR BELTS. MODELS HAVE COME INTO
BETTER AGREEMENT REGARDING THE INCOMING STORM SYSTEM WHICH NOW
TRACK THE SURFACE LOW OVER THE KITTITAS VALLEY...ALONG THE I-90
CORRIDOR...BEFORE TRACKING TO THE NORTHEAST ACROSS THE NORTHERN
IDAHO PANHANDLE INTO SOUTHEASTERN BRITISH COLUMBIA. THE LOW WILL
BOTTOM OUT THIS EVENING WHILE CROSSING ONTO THE WASHINGTON COAST
JUST BELOW 990MB...THEN GRADUALLY FILL AND WEAKEN OVERNIGHT INTO
TOMORROW. THE HEAVIEST PRECIPITATION OVERNIGHT WILL FOCUS ALONG
THE CASCADES...WATERVILLE PLATEAU...OKANOGAN REGION...AS THE LOW
NEARS THE COAST TONIGHT AND INCREASING EASTERLY FLOW ENHANCES LIFT
UNDER A BLANKET OF DEEP ISENTROPIC ASCENT. AS THE LOW JUMPS THE
CASCADES AFT 12Z SUNDAY...THE PRECIPITATION SHIELD WILL BEGIN TO
SHIFT TOWARD FAR EASTERN WASHINGTON AND IDAHO. RADAR IMAGERY WILL
LIKELY ILLUSTRATE A WELL DEFINED DEFORMATION BAND ALONG THE
NORTHERN PERIPHERY OF THE LOW WHICH IS WHERE THE 6 HOUR LIQUID
AMTS WILL NEAR THREE-TENTHS OF AN INCH THEN AS THE LOW EJECTS TO
NORTHEAST MIDDAY TOMORROW...CONTINUED STRONG UPSLOPE INTO THE ID
PANHANDLE WILL RESULT IN THE SECOND CHANCE FOR MODERATE
PRECIPITATION RATES...MAINLY FOCUSING INTO THE PANHANDLE
MTNS...IDAHO PALOUSE...AND COEUR D ALENE AREA. SNOWFALL TOTALS
WILL GENERALLY RUN 2-5 INCHES IN THE VALLEYS WITH 6-10" IN THE
MOUNTAINS. WITH THE HIGHEST TOTALS ACROSS THE CENTRAL ID PANHANDLE
AS THE SECOND WAVE OF PRECIPITATION FORMS IN THE WAKE OF THE LOW.
THIS IS WHERE WINTER WEATHER WARNINGS WERE POSTED AND VALLEYS CAN
EXPECT 3-6" WITH 8-10" IN THE MOUNTAINS.
CURRENT OBSERVATIONS FROM THE EAST SLOPES...OKANOGAN HIGHLANDS...AND
WENATCHEE AREA SUGGEST TEMPERATURES HAVE WARMED INTO THE MID TO
UPPER 40`S BELOW 2000` WITH DEWPOINTS IN THE UPPER 20`S TO LOWER
30`S. CALCULATED WETBULB COOLING SUGGEST TEMPERATURES WILL REMAIN
IN THE MID TO UPPER 30`S WITH THE ONSET OF PRECIPITATION SO ALL
WINTER HIGHLIGHTS IN THE AFOREMENTIONED ZONES WERE FOCUSED MAINLY
ABOVE 2000`.
WINDS WILL BE BREEZY THROUGH THE PERIOD WITH THE HIGHEST GUSTS
EXPECTED SUNDAY AFTERNOON UNDER THE COLD ADVECTION REGIME. MODELS
CONTINUE TO HINT 850MB WINDS OF 35-50KTS DOWN THE EAST SLOPES AND
THIS WILL NEED TO BE MONITORED CLOSELY. THESE BREEZY WINDS WILL
ALSO CAUSE AREAS OF BLOWING SNOW AT TIMES BUT WITH THE SNOW BEING
OF A WETTER NATURE...EXPECT THIS WILL BE LOCALIZED. /SB
SUNDAY NIGHT THROUGH TUESDAY NIGHT...MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT THE PERIOD WILL BEGIN ON A QUIETING NOTE AS
SUNDAYS UPPER LEVEL TROF SHIFTS INTO CENTRAL MONTANA. THE TROF
WILL BE SLOWLY REPLACED BY A WELL-DEFINED UPPER LEVEL RIDGE
RESULTING IN RAPID STABILIZATION OVER THE ENTIRE REGION. THUS THE
POST-FRONTAL SHOWERS OVER THE IDAHO PANHANDLE DUE TO MOIST UPSLOPE
SW FLOW WILL DECREASE RAPIDLY. MODEL CROSS SECTIONS SHOW THE
POTENTIAL INSTABILITY DECREASING FROM AROUND 550 MBS AT 00Z TO
LESS THAN 700 MBS BY 12Z. MEANWHILE RELATIVE HUMIDITY VALUES
DECREASE RAPIDLY ABOVE 700 MBS AS WELL. THIS SUGGESTS THAT MOST OF
THE POST-FRONTAL SHOWER ACTIVITY OVER THE CENTRAL PANHANDLE WILL
DECREASE AFTER 06Z WITH ONLY A FEW PERSISTENT SHOWERS .
GENERALLY DRY WEATHER WILL THEN PERSIST THROUGH MOST OF MONDAY UNTIL
ANOTHER FRONT PUSHES INTO WESTERN WASHINGTON LATE IN THE DAY.
MOISTURE ASSOCIATED WITH THIS DISTURBANCE WAS CURRENTLY LOCATED
JUST WEST OF 150W AND WAS ADEQUATELY HANDLED BY BOTH THE GFS AND
ECMWF AS OF 22Z. BOTH MODEL SOLUTIONS BRING THE PRE-FRONTAL UPPER
LEVEL RIDGE INTO NORTH IDAHO BY 00Z TUE WITH A SWIFT MOVING
SHORTWAVE TROF PASSING THROUGH THE SOUTHERN THIRD OF BC OVERNIGHT.
THIS SYSTEM SHOULD BE MUCH LESS DYNAMIC AND IMPRESSIVE THAN THE
ONE EXPECTED TONIGHT AND SUNDAY. IN FACT...THE MODELS HAVE BEEN
TRENDING TOWARD KEEPING THE PRECIPITATION FAIRLY LIGHT WITH MOST
OF IT HOLDING OVER THE NORTHERN THIRD OF THE CWA. GIVEN THE TRACK
OF THE UPPER LEVEL TROF...THE PRIMARY FLOW IN THE 850-700 MB LAYER
WILL REMAIN OUT OF THE WEST SO WITHOUT THE BENEFIT OF A STRONG
WARM FRONT OR ISENTROPIC ASCENT WE WOULD ALSO EXPECT TO SEE A FAIR
AMOUNT OF DOWNSLOPE FLOW OVER THE CASCADES. WHILE BOTH THE GFS AND
ECMWF DO HINT AT A WEAK WARM AIR ADVECTION PATTERN IN THE 850-700
MB LAYER ITS NOT NECESSARILY ENOUGH TO OVERCOME THE DOWNSLOPE
IMPACTS OF THE CASCADES. WHILE THIS SYSTEM WONT HAVE THE BENEFIT
OF STRONG DYNAMICAL FORCING IT WILL FEATURE A HIGH AMOUNT OF
MOISTURE...AS EVIDENCED BY PRECIPITABLE WATER VALUES AROUND
150-180 PERCENT OF NORMAL. THERE WILL ALSO BE PERSISTENT WEAK
ISENTROPIC ASCENT. WHATS INTERESTING IN THIS SCENARIO IS THE FRONT
LOSES MUCH OF ITS EASTWARD MOMENTUM AS YET ANOTHER SYSTEM PUSHES
INTO THE COAST BY LATE TUESDAY. THIS NEXT SYSTEM AMPLIFIES YET
ANOTHER SHORTWAVE RIDGE OVER THE AREA...WHICH ALLOWS THE MONDAY
FRONT TO SIT AND GRADUALLY WEAKEN OVER THE REGION AND SHIFT SLOWLY
SOUTH THROUGH TUESDAY . GIVEN THIS SCENARIO WE WOULD EXPECT TO SEE
A LIGHT AND RATHER PROLONGED STRATIFORM PRECIPITATION EVENT MUCH
OF WHICH WILL FALL AS SNOW. GIVEN THE WEAK FORCING WE PREFER THE
DRIER GFS AND ECMWF SOLUTIONS OVER THE RATHER WET NAM. AT THIS
POINT IT APPEARS WINTER HIGHLIGHTS WILL NOT BE NECESSARY. MOST OF
THE PRECIPITATION IS EXPECTED TO FALL NORTH OF I90. FX
WEDNESDAY TO SATURDAY...THE MEDIUM-RANGE STARTS WITH A RIDGE OVER
THE WEST...A WARM FRONT NR THE BC BORDER AND A COLD FRONT NR 130W.
THIS LEAVES PASSING MID/HIGHER CLOUDS AND A CHANCE OF RAIN AND SNOW
ACROSS THE CASCADES AND WA/BC BORDER MTNS INTO WED NT...WITH SOME
EARLY FOG/STRATUS THREAT. THEREAFTER MODELS DIVERGE OVER COLD FRONT
PASSAGE. THE FCST LEANS TO THE GFS...WITH BETTER CONSISTENCY AND
GEM/DGEX AGREEMENT. THE ECMWF TRENDED TO GFS. ALL THIS TRANSLATES
TO THE COLD FRONT PUSHING TO THE CASCADES THU AM AND EAST THU NT
INTO FRI AM...INCREASING PRECIP CHANCES. A THREAT FOR OROGRAPHIC
RAIN/SNOW SHOWERS CONTINUES FRIDAY BEFORE THE NEXT SYSTEM APPROACHES
LATER SATURDAY. SLIGHTLY ABOVE NORMAL TEMPERATURES WEDNESDAY TREND
CLOSER TO NORMAL BY SATURDAY. /JCOTE
&&
.AVIATION...
A WEAK RIDGE ALOFT WILL PROMOTE VFR CONDITIONS AT ALL TAF SITES
THROUGH 03Z TONIGHT...WITH LINGERING SNOW SHOWERS LOCALLY
OBSCURING MOUNTAINS IN THE IDAHO PANHANDLE AND CASCADE CREST.
THE NEXT PACIFIC STORM SYSTEM WILL SPREAD IFR CEILINGS TO THE
WESTERN REACHES OF THE REGION AFTER 04Z...SPREADING INTO THE
EASTERN TERMINALS AFT 10Z. THE INCOMING STORM SYSTEM WILL
ALSO TIGHTEN PRESSURE GRADIENTS LEADING TO INCREASING WINDS
FROM KPUW-KGEG WITH GUSTS OF 25-35KTS.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 31 37 25 38 30 40 / 80 90 10 20 40 20
COEUR D`ALENE 30 38 27 39 30 40 / 50 90 20 20 50 20
PULLMAN 31 37 27 40 29 44 / 70 90 10 10 30 20
LEWISTON 35 42 31 47 32 49 / 40 90 20 10 20 20
COLVILLE 32 40 27 39 29 40 / 80 100 10 50 60 10
SANDPOINT 30 37 27 34 27 36 / 30 90 20 50 60 40
KELLOGG 29 33 28 33 29 37 / 30 100 70 20 50 30
MOSES LAKE 31 44 24 43 26 45 / 100 50 0 30 30 0
WENATCHEE 32 43 29 43 32 45 / 100 50 0 30 40 0
OMAK 31 43 22 41 29 45 / 100 80 0 70 80 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...WINTER WEATHER ADVISORY FROM 4 AM TO 10 PM PST SUNDAY FOR
NORTHERN PANHANDLE.
WINTER STORM WARNING FROM 4 AM SUNDAY TO 1 AM PST MONDAY FOR
CENTRAL PANHANDLE MOUNTAINS.
WINTER STORM WARNING FROM 4 AM TO 10 PM PST SUNDAY FOR COEUR
D`ALENE AREA...IDAHO PALOUSE.
WA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON PST
SUNDAY FOR OKANOGAN HIGHLANDS.
WINTER WEATHER ADVISORY FROM 4 AM TO 10 PM PST SUNDAY FOR
NORTHEAST BLUE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 4 AM TO 4 PM PST SUNDAY FOR
NORTHEAST MOUNTAINS...SPOKANE AREA...WASHINGTON PALOUSE.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON PST
SUNDAY FOR UPPER COLUMBIA BASIN.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
SUNDAY FOR OKANOGAN VALLEY...WATERVILLE PLATEAU...WENATCHEE
AREA.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
SUNDAY FOR EAST SLOPES NORTHERN CASCADES.
&&
$$
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000
FXUS66 KPQR 212226
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
220 PM PST SAT NOV 21 2009
.SYNOPSIS...A STRONG PACIFIC FRONTAL SYSTEM IS APPROACHING THE COAST
THIS AFTERNOON WITH A WARM FRONT MOVING INLAND THIS AFTERNOON AND
EVENING...AND THE ASSOCIATED COLD FRONT QUICKLY FOLLOWING TONIGHT AS
A SURFACE LOW PRESSURE SYSTEM MOVES INLAND NEAR THE WA OREGON BORDER.
A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUN AFTERNOON AND
NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES MON.
&&
.SHORT TERM...MODELS ARE STILL SHOWING DIFFERENCES IN TRACK OF THE
SURFACE LOW COMING IN TONIGHT. THE GENERAL CONSENSUS IS TO BRING IT
IN JUST NORTH OF THE WASHINGTON/OREGON BORDER. MODELS ARE IN BETTER
AGREEMENT ON THE UPPER FEATURES...WITH A STRONG SHORTWAVE MOVING
ACROSS THE FORECAST AREA TONIGHT...DIGGING TO THE ESE. TIMING OF THE
COLD FRONT IN ALL MODELS INDICATES FRONTAL PASSAGE ON THE COAST
AROUND MIDNIGHT TONIGHT. HAVE UPGRADED THE HIGH WIND WATCH FOR THE
ENTIRE COAST TO A HIGH WIND WARNING. WINDS INLAND LOOK GUSTY WITH AND
BEHIND THE FRONT AS THERE ARE STRONG PRESSURE RISES BEHIND THE
FRONT...WILL ISSUE AN ADVISORY FOR THE WILLAMETTE VALLEY..I-5
CORRIDOR AND THE LOWER COLUMBIA FOR TONIGHT AND EARLY SUNDAY MORNING
WITH THE AFTERNOON PACKAGE.
DOPPLER RADAR INDICATES THAT SHOWERS HAVE SIGNIFICANTLY DIMINISHED
OVER THE AREA WITH ONLY AN ISOLATED SHOWER OR TWO OVER THE SOUTH
WASHINGTON CASCADES AND HAVE ALREADY CANCELLED THE SNOW ADVISORY FOR
THE CASCADES. WILL CONTINUE THE WINTER STORM WARNING FOR THE
CASCADES AS MOISTURE...STRENGTH OF THE FRONT AND THE POST FRONTAL
FLOW ALL FAVOR SIGNIFICANT SNOWFALL FOR LATER TONIGHT AND SUN.
A WEAK UPPER RIDGE WILL BUILD OVER THE FORECAST AREA SUNDAY NIGHT AND
MONDAY FOLLOWING THE FRONT. BEST CHANCES FOR PRECIPITATION MONDAY AND
TUESDAY WILL SHIFT N INTO WA WITH WARM FRONT OVERRUNNING. THE UPPER
RIDGE HOLDS COLD FRONT AT BAY UNTIL AFTER TUE NIGHT. LIKENS
.LONG TERM...WEAK HIGH PRES RIDGE OVER THE FORECAST AREA CONTINUES TO
PUSH ENERGY NORTH OF FORECAST AREA MID WEEK. IT MANAGES TO DELAY THE
ARRIVAL OF A SECOND SYSTEM THROUGH THUR. MODEL SOLUTIONS DIVERGE
TOWARD THE END OF THE WEEK AND HAVE LITTLE CONFIDENCE IN THEM. AT
THIS TIME WILL GO WITH CLIMATOLOGY UNTIL THERE IS SOME CONSISTENCY
BETWEEN THE MODELS..
&&
.AVIATION...PREDOMINATELY VFR WITH SCATTERED SHOWERS...WHICH MAY
BRING VERY BRIEF MVFR CIGS. CONDITIONS REMAIN VFR THIS
AFTERNOON...THOUGH WILL SEE INCREASING MVFR ALONG THE COAST AS WARM
FRONT SWINGS ACROSS THE REGION. COLD FRONT TONIGHT WILL BRING
INCREASING MVFR AFTER 04Z...AND INCREASING SOUTHERLY WINDS SOME OF
WHICH MAY BE QUITE STRONG IN SOME AREAS. LOCATION OF STRONG WINDS
WILL DEPEND ON WHERE THE LOW COMES INLAND.
KPDX AND APPROACHES...VFR CONDITIONS THROUGH 05Z...THEN INCREASING
MVFR CIGS AS COLD FRONT APPROACHES. WATCH FOR POTENTIAL OF LOW LEVEL
WIND SHEAR BETWEEN 06Z AND 18Z TONIGHT AND TOMORROW MORNING AS WILL
SEE INCREASING SOUTH WINDS ALOFT...BLOWING OVER THE LOW LEVEL
EASTERLY FLOW COMING FROM GORGE. SOUTH TO SOUTHWEST WINDS MAY BE
QUITE STRONG AROUND 12Z AS STRONG GRADIENT DEVELOPS OVER NORTH
VALLEY AS LOW MOVES INLAND. WIND GUSTS NEAR 50 TO 55 MPH ARE
POSSIBLE. WOLFE
&&
.MARINE...GALE FORCE SOUTH WINDS WILL STRENGTHEN TO STORM FORCE AS
POTENT LOW MOVES OVER THE COASTAL WATERS. STORM WARNING FOR THE
COASTAL WATERS FOR TONIGHT. WINDS TURN MORE W TO NW ON SUNDAY AND
BEGIN EASING. SEAS TONIGHT LIKELY TO PEAK IN THE 20 TO 25 FT
RANGE...BUT WILL DROP QUICKLY TO THE MID TEENS ON SUN.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR THIS AFTERNOON.
STORM WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR TONIGHT.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS
THROUGH SUN.
WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
CASCADES TONIGHT AND SUNDAY.
HIGH WIND WARNING FOR THE SOUTHERN WASHINGTON/NORTHERN AND
CENTRAL OREGON COAST TONIGHT.
WIND ADVISORY FOR THE WILLAMETTE VALLEY..THE LOWER
COLUMBIA..AND THE I-5 CORRIDOR FOR THIS EVENING THROUGH
SUNDAY MORNING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
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000
FXUS66 KSEW 211915 AAA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1113 AM PST SAT NOV 21 2009
.SYNOPSIS...A WEAK UPPER LEVEL RIDGE WILL MOVE OVER WESTERN
WASHINGTON THROUGH MIDDAY TODAY...FOLLOWED QUICKLY BY A VIGOROUS
FRONTAL SYSTEM THIS AFTERNOON AND EVENING BRINGING RAIN AND WINDY
CONDITIONS TO THE AREA INTO SUNDAY. HEAVY SNOW WILL FALL IN THE
MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW 3000 FEET. A
WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND MONDAY
NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATER IN THE WEEK.
&&
.SHORT TERM...NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON AND
LINGERING SCATTERED SHOWERS ACROSS THE AREA THIS MORNING. THE
FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT. THE WEAK OFFSHORE RIDGE
WILL CONTINUE TO MOVE QUICKLY ACROSS WESTERN WASHINGTON THIS
MORNING...FOLLOWED BY THE SOUTH END OF AN OCCLUDED FRONT SWINGING
INTO BRITISH COLUMBIA BRINGING SIGNIFICANT PRECIPITATION TO THE THE
COAST AND OLYMPICS THIS AFTERNOON. A FRONTAL WAVE AND STRONG JET
WILL 45N/145W WILL DEEPEN AND MOVE THROUGH THE FORECAST AREA
TONIGHT.
HEAVY SNOW FOR THE MOUNTAINS REMAINS ON TRACK WITH IMPRESSIVE
PRECIPITATION AMOUNTS OVER THE OLYMPICS IN THE 3 TO 4 INCH RANGE AND
THE CASCADES IN THE 1 TO 3 INCH NEIGHBORHOOD THROUGH SUNDAY MORNING.
SNOW LEVELS RISE TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...
WITH ROUGHLY TO 30 TO 40 INCHES OF SNOW EXPECTED FOR THE OLYMPICS
AND 10 TO 30 INCHES FOR THE CASCADES. EVEN THE RELATIVELY DRIER
HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS.
THE TRACK OF THE SURFACE LOW REMAINS ONE OF THE FORECAST CHALANGES
FOR THE DAY. THE MOST LIKELY SCENARIO REMAINS THAT IT WILL REACH THE
CENTRAL WASHINGTON COAST AROUND MIDNIGHT TONIGHT...MOVE NORTHEAST
ACROSS THE OLYMPIC PENINSULA AND INTO THE NORTH PART OF THE PUGET
SOUND REGION TO AROUND MT BAKER AT 4 AM AND THEN HEAD INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS ACROSS THE
AREA. STONGEST WINDS WILL LIKELY BE WITH THE SOUTHERLIES AHEAD OF
THE LOW TONIGHT ESPECIALLY ALONG THE COAST AND NORTHWEST
INTERIOR...AND AGAIN WITH THE WESTERLIES SUNDAY MORNING THROUGH THE
EAST STRAIT INTO WHIDBEY ISLAND. FOR NOW HAVE ISSUED A HIGH WIND
WATCH FOR THE CENTRAL WASHINGTON COAST THROUGH THE CHEHALIS GAP AND
INTO THE SOUTHWEST INTERIOR FOR THE STRONG WESTERLIES WITH THE LOW
SUNDAY MORNING. IN ADDITION HAVE ISSUED A WIND ADVISORY FOR THE
NORTH INTERIOR...ADMIRALTY INLET...SAN JUANS AND EAST STRAIT FOR THE
SOUTHERLIES THIS AFTERNOON AND TONGITH FOLLOWED BY THE WESTERLIES
WITH AND BEHIND THE LOW. WILL BE WATCHING EVOLUTION AND TRACK OF THE
LOW AS IT APPROACHES THE COAST THIS AFTERNOON. WINDS SHOULD BEGIN TO
COME DOWN BY LATE SUNDAY MORNING ALL AREAS.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON EVENING AS AN
UPPER RIDGE WILL MOVE OVERHEAD SUNDAY EVENING. THE RIDGE KICKS EAST
QUICKLY MONDAY AHEAD OF ANOTHER FRONTAL SYSTEM. THIS SYSTEM COULD
STILL BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT WEAKENS AS IT MOVES INLAND MONDAY
NIGHT. COMPARED TO LAST SEVERAL SYSTEMS THIS WILL BE AN UNEVENTFUL
SYSTEM...MARKING THE BEGINNING OF A PERIOD OF QUIETER WEATHER. COOK
.LONG TERM...FROM PREVIOUS DISCUSSION...A WEAK UPPER RIDGE WILL
FOLLOW THE FRONT THAT MOVES THROUGH MONDAY AND MONDAY NIGHT. THERE
IS JUST A CHANCE OF RAIN IN THE FORECAST FOR TUESDAY AND
WEDNESDAY...WITH A FAIRLY GOOD CHANCE FOR SOME DRY WEATHER OVER
THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY MOVE ACROSS WESTERN
WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER FRONTAL WAVE WILL
PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND FRIDAY...THOUGH
DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY BY LATE IN THE
WEEK. MCDONNAL
&&
.HYDROLOGY...TODAYS SYSTEM WILL BRING IMPRESSIVE AMOUNTS OF
PRECIPITATION TO THE CASCADES AND OLYMPICS...BUT RELATIVELY LOW SNOW
LEVELS WILL MITIGATE THE IMPACT ON RIVERS EXCEPT THE TWO RIVERS THAT
ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND THE
LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. THE SNOW LEVEL
WILL ONLY RISING TO AROUND 3000 FT...MAKING THIS MOSTLY A MOUNTAIN
SNOW EVENT AND NOT A RAIN EVENT.
THE SKOKOMISH RIVER HAS FALLEN TO NEAR OR JUST BELOW FLOOD STAGE AT
THIS TIME...NEW FORECAST GUIDANCE SHOWS THE RIVER RISING AGAIN TO
JUST BELOW 17 FEET BY EARLY SUNDAY MORNING. IN ADDITION...THERE WILL
BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM #2 INTO THE NORTH
FORK SKOKOMISH RIVER THIS AFTERNOON. ACCORDINGLY WILL EXTEND THE
WARNING FOR THE SKOKOMISH INTO MONDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT REMAINS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY LOOKS TO BE PROGRESSIVE ENOUGH AND WEAK
ENOUGH TO BE OF LITTLE CONCERN WITH RESPECT TO FLOODING. THE AIR
MASS OVER THE NORTHWEST FOR THE REMAINDER OF THE WEEK WILL BE WARMER
WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE EXPECTED TO
AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED TO CAUSE
ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. COOK
&&
.AVIATION...A WARM FRONT WILL SPREAD RAIN INTO WRN WA THIS AFTERNOON
THROUGH TONIGHT. SW FLOW ALOFT WILL INCREASE THROUGH THE DAY AND
BECOME STRONG SLY FLOW BY THIS EVENING. THE ATMOSPHERE WILL REMAIN
MOIST AND STABLE.
A STRONG SURFACE LOW WILL DEVELOP OFFSHORE TODAY AND
TONIGHT...REACHING THE S OR CENTRAL WA COAST BY 12Z SUN MORNING AS A
POTENTIAL 985 MB LOW. THIS WILL BRING STRONG SLY FLOW ALOFT AND AT
THE SURFACE...SHIFTING WLY AFTER 12Z AS THE LOW TRACKS INLAND NEAR
KHQM...PROBABLY TRACKING JUST SOUTH OF KOLM. HOWEVER...THE TRACK IS
UNCERTAIN AT THIS TIME WITH SOME MODELS SHOWING A MORE NORTHERN
SOLUTION.
KSEA...SLY WINDS 8-15 KT TODAY...BECOMING MORE ELY TONIGHT. THERE
WILL BE A POTENTIAL FOR LLWS BETWEEN 03Z AND 12Z SUN DUE TO ELY
WINDS AT THE SFC AND STRONG SLY WINDS NEAR 2K FT. CONFIDENCE IS
STILL LOW BUT MAY WILL MONITOR AND IF NEEDED UPDATE THE TAF PRIOR TO
THE 00Z ISSUANCE. LATEST 12Z MODEL SOLUTIONS CONTINUE TO VARY
CONSIDERABLE REGARDING THE TRACK AND DEPTH OF A SURFACE LOW NOW
EXPECTED TO AFFECT THE AREA. WINDS WILL INCREASE DRAMATICALLY FROM
THE SW SOMETIME BETWEEN 12Z AND 15Z. CONCERNING CIGS...ANTICIPATE
CIGS TO GRADUALLY LOWER DURING THE DAY...ALTHOUGH THERE WILL BE
OCCASIONAL CIGS NEAR 2500 FT THIS MORNING. BY LATE THIS
EVENING...CIGS SHOULD BE NEAR 2K FT...WITH RAIN AND FOG REDUCING
VSBYS INTO THE 3-5SM RANGE. DTM
&&
.MARINE...WINDS WILL PICK UP ALONG THE COAST BY MIDDAY AND ACROSS
THE INLAND WATERS DURING THE AFTERNOON AS A WARM FRONT REACHES
WESTERN WASHINGTON. LATEST MODELS SHOW GALES TO DEVELOP WITH THIS
INITIAL FRONT FROM AROUND THE E ENTRANCE/ADMIRALTY INLET NWD AND
ALSO THE COASTAL WATERS. WIND ADVISORY FOR THE SOUND STILL LOOKS
GOOD.
A POTENTIALLY STRONG 985 MB SURFACE LOW WILL ENTER THE COASTAL
WATERS AFTER 09Z TONIGHT AND TRACK INTO THE CENTRAL/S WA COAST
AROUND 12Z. WINDS BEHIND THE FRONT WILL RISE DRASTICALLY SO I UPPED
THE WINDS TO HIGH END GALE AND EXTENDED THE WARNING THROUGH SUN
MORNING. DEPENDING ON THE EXACT TRACK...STORM FORCE WINDS COULD BE
POSSIBLE ACROSS THE CENTRAL/S WA COASTAL WATERS. WILL EVALUATE THIS
POSSIBILITY BEFORE THE AFTERNOON COASTAL FORECAST ISSUANCE. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR
A PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
WIND ADVISORY IN EFFECT FOR THE NORTH INTERIOR...EAST
STRAIT...AND ADMIRALTY INLET THROUGH SUNDAY MORNING.
HIGH WIND WATCH IN EFFECT FOR THE CENTRAL COAST...LOWER
CHEHALIS...AND SOUTHWEST INTERIOR FROM LATE TONIGHT THROUGH
SUNDAY MORNING...
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS...AND
FROM ADMIRALTY INLET NORTHWARD THROUGH EARLY SUN MORNING.
.A GALE WATCH IS IN EFFECT FOR THE CENTRAL AND
EAST STRAIT...AND ADMIRALTY INLET FROM EARLY
SUN MORNING THROUGH SUNDAY AFTERNOON.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR PUGET SOUND FROM
NOON THROUGH SUNDAY MORNING.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 211810
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1010 AM PST SAT NOV 21 2009
.SYNOPSIS...
AFTER A SHORT RELATIVELY QUIET BREAK IN THE WEATHER TODAY...A
STRONGER AND COLDER STORM SYSTEM WILL BRING THE POTENTIAL FOR
MODERATE TO HEAVY SNOWFALL OVER MUCH OF THE REGION TONIGHT AND
SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO PASS THROUGH
THE INLAND NORTHWEST EVERY 24 TO 36 HOURS THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...
QUICK UPDATE THIS MORNING TO DECREASE CLOUDS AND POPS ACROSS THE
BASIN AND NORTHERN VALLEYS. VISIBLE SATELLITE IMAGERY SHOWING
VERY LITTLE IN THE WAY OF CLOUDS AT THIS HOUR AND SHOWER ACTIVITY
IS MAINLY CONFINED TO THE HIGHER TERRAIN OF THE CASCADES AND IDAHO
PANHANDLE. WATER VAPOR IMAGERY SHOWING A FAST MOVING STORM SYSTEM
BEGINNING TO TAKE SHAPE OUT NEAR 135W 45N WHICH WILL BRING OUR
NEXT ROUND OF WINTRY WEATHER OVERNIGHT INTO SUNDAY.
&&
.AVIATION...
A WEAK RIDGE ALOFT WILL PROMOTE VFR CONDITIONS AT ALL TAF SITES
THROUGH 03Z TONIGHT...WITH LINGERING SNOW SHOWERS LOCALLY
OBSCURING MOUNTAINS IN THE IDAHO PANHANDLE AND CASCADE CREST.
THE NEXT PACIFIC STORM SYSTEM WILL SPREAD IFR CEILINGS TO THE
WESTERN REACHES OF THE REGION AFTER 04Z...SPREADING INTO THE
EASTERN TERMINALS AFT 10Z. THE INCOMING STORM SYSTEM WILL
ALSO TIGHTEN PRESSURE GRADIENTS LEADING TO INCREASING WINDS
FROM KPUW-KGEG WITH GUSTS OF 25-35KTS.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 39 32 37 27 39 31 / 10 70 90 10 40 10
COEUR D`ALENE 39 31 37 28 40 31 / 20 60 90 20 50 20
PULLMAN 40 32 36 28 42 32 / 20 60 90 20 40 20
LEWISTON 47 36 41 30 48 35 / 10 60 90 20 30 20
COLVILLE 39 33 40 28 38 30 / 10 100 90 10 60 20
SANDPOINT 33 32 37 28 36 30 / 40 90 90 20 60 30
KELLOGG 32 30 34 27 35 30 / 70 70 100 40 60 40
MOSES LAKE 45 32 43 26 43 30 / 10 80 50 0 40 10
WENATCHEE 43 32 43 29 41 33 / 10 90 50 10 50 10
OMAK 43 31 42 25 40 27 / 10 100 50 0 60 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
COEUR D`ALENE AREA.
WINTER STORM WATCH FROM 6 PM PST THIS EVENING THROUGH SUNDAY
MORNING FOR NORTHERN PANHANDLE.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY AFTERNOON
ABOVE 2500 FEET FOR CENTRAL PANHANDLE MOUNTAINS.
WA... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
SPOKANE AREA.
WINTER STORM WATCH FROM 6 PM PST THIS EVENING THROUGH SUNDAY
MORNING FOR EAST SLOPES NORTHERN CASCADES.
WINTER STORM WATCH FROM 6 PM PST THIS EVENING THROUGH SUNDAY
MORNING ABOVE 2000 FEET FOR NORTHEAST MOUNTAINS...OKANOGAN
HIGHLANDS.
WINTER STORM WATCH FROM 6 PM PST THIS EVENING THROUGH SUNDAY
MORNING ABOVE 2000 FEET FOR OKANOGAN VALLEY...UPPER
COLUMBIA BASIN...WATERVILLE PLATEAU.
&&
$$
000
FXUS66 KPQR 211718
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
917 AM PST SAT NOV 21 2009
...UPDATED FOR HIGH WIND WATCH AND POSSIBLE WIND ADVISORY IN THE
WILLAMETTE VALLEY TONIGHT...
.SYNOPSIS...A WARM FRONT WILL APPROACH THE OREGON COAST THIS
AFTERNOON THEN PUSH INLAND THIS EVENING. A COLD FRONT WILL QUICKLY
FOLLOW TONIGHT AS A SURFACE LOW PRESSURE SYSTEM MOVES INLAND NEAR THE
WA OREGON BORDER. A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUN
AFTERNOON AND NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES MON.
&&
.SHORT TERM...LATEST MODEL RUNS CONTINUE TO EXHIBIT DIFFERENCES IN
TRACK OF THE SURFACE LOW COMING IN TONIGHT. UPPER FEATURES APPEAR
PRETTY WELL AGREED ON...WITH A STRONG SHORTWAVE MOVING ACROSS THE
FORECAST AREA TONIGHT...DIGGING TO THE ESE. GIVEN THE TRACT OF THE
UPPER VORT MAX AND THE NEGATIVE TILT OF THE UPPER TROUGH...CONTINUE
TO PREFER A MORE SOUTHERLY TRACK OF THE SURFACE LOW...AS SUCH PREFER
THE 00Z RUN OF THE ECMWF WHICH TAKES A SURFACE LOW E ROUGHLY ACROSS
KKLS AT 12Z SUN. TIMING OF THE COLD FRONT IN ALL MODELS INDICATES
FRONTAL PASSAGE ON THE COAST NOT UNTIL SOMETIME TONIGHT. GIVEN THE
CONTINUED UNCERTAINTIES IN THE MODELS...WILL EXTEND THE HIGH WIND
WATCH FOR THE N AND CENTRAL OREGON COAST TO INCLUDE THE SOUTHERN
WASHINGTON COAST...AND EXTEND IT TILL 6AM. WINDS INLAND LOOK GUSTY
WITH AND BEHIND THE FRONT AS THERE ARE STRONG PRESSURE RISES BEHIND
THE FRONT...EXPECT AN ADVISORY FOR SOME PORTION OF THE WILLAMETTE
VALLEY FOR LATE TONIGHT WILL BE NEEDED...WILL PROBABLY ISSUE WITH
AFTERNOON PACKAGE.
DOPPLER RADAR CONTINUES TO SHOW SHOWERS SPREADING OVER MOST OF THE
FORECAST AREA THIS MORNING AS WESTERLY FLOW ALOFT FOLLOWS THE UPPER
TROUGH. WITH UPPER RIDGING LATER TODAY...AND LOW LEVEL FLOW BACKING
MORE TO THE S...SHOULD SEE SHOWERS DROP OFF TODAY. OVERNIGHT SNOWFALL
AMOUNTS IN THE CASCADES SINCE LAST EVENING HAVE RANGED FROM ROUGHLY 4
TO 9 INCHES. FOR NOW WILL HANG ONTO THE SNOW ADVISORY FOR THE N
OREGON AND S WA CASCADES TODAY...ALTHOUGH WILL LIKELY SEE A
SIGNIFICANT DROPOFF IN SNOWFALL LATER THIS MORNING. WILL CONTINUE
THE WINTER STORM WARNING FOR THE CASCADES AS MOISTURE...STRENGTH OF
THE FRONT AND THE POST FRONTAL FLOW ALL FAVOR SIGNIFICANT SNOWFALL
LATER TONIGHT AND SUN.
CURRENT MODEL RUNS INDICATE BEST CHANCES FOR PRECIPITATION MONDAY
WILL SHIFT N INTO WA WITH WARM FRONT OVERRUNNING. THE UPPER RIDGE
HOLDS COLD FRONT AT BAY UNTIL MON NIGHT. LIKENS
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...WEAK HIGH PRES
BUILDS OVER THE FORECAST AREA MON NIGHT. MODELS SHOW A WEAK SYSTEM
APPROACH THE COAST EARLY TUE...BUT IT TRACKS FURTHER NORTH AND
LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF THE CWA. THIS RIDGE IS
MORE PERSISTENT THAN PREVIOUS MODEL RUNS SUGGESTED. IT MANAGES TO
DELAY THE ARRIVAL OF A SECOND SYSTEM THROUGH THUR. BY MID NEXT
WEEK...MODELS DISAGREE ON THE SOLUTION FOR THE WEEKEND. GFS MODEL
RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK ON PRECIP THROUGH THURS
NIGHT BUT THE CURRENT RUN SHOWS RAIN EXTENDING TO THE CASCADES THURS
NIGHT. SO FAR...MODELS SUGGEST A FAIRLY NICE WEEKEND AS ANOTHER UPPER
HIGH PRES TEMPORARILY SETS UP OVER THE PAC NW. LRAMIREZ
&&
.AVIATION...LITTLE CHANGE IN OVERALL CONDITIONS THIS MORNING.
PREDOMINATELY VFR WITH SCATTERED SHOWERS...WHICH MAY BRING VERY
BRIEF MVFR CIGS. CONDITIONS REMAIN VFR THROUGH TODAY...THOUGH WILL
SEE INCREASING MVFR ALONG THE COAST AFTER 20Z AS WARM FRONT SWINGS
ACROSS THE REGION. COLD FRONT TONIGHT WILL BRING INCREASING MVFR
AFTER 04Z...AND INCREASING SOUTHERLY WINDS.
KPDX AND APPROACHES...VFR CONDITIONS THROUGH 05Z...THEN INCREASING
MVFR CIGS AS COLD FRONT APPROACHES. WATCH FOR POTENTIAL OF LOW LEVEL
WIND SHEAR BETWEEN 00Z AND 06Z TONIGHT AS WILL SEE INCREASING SOUTH
WINDS ALOFT...BLOWING OVER THE LOW LEVEL EASTERLY FLOW COMING FROM
GORGE.ROCKEY/WOLFE
&&
.MARINE...NOT MUCH CHANGE. CONDITIONS WILL DETERIORATE LATER TODAY
AS WARM FRONT LIFTS ACROSS THE REGION. THIS WILL BRING GALE FORCE
SOUTH WINDS. HOWEVER...STRONG WINDS ARRIVE TONIGHT AS RATHER STRONG
LOW PRES PASSES ACROSS THE N OREGON COASTAL WATERS. STORM WARNING
FOR THE COASTAL WATERS FOR TONIGHT. WINDS TURN MORE W TO NW ON
SUNDAY AND BEGIN EASING. SEAS TONIGHT LIKELY TO PEAK IN THE 20 TO 25
FT RANGE...BUT WILL DROP QUICKLY ON SUN.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR THIS AFTERNOON.
STORM WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR TONIGHT.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS
THROUGH SUN.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES THROUGH 4 PM.
WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
CASCADES TONIGHT AND SUNDAY.
HIGH WIND WATCH FOR THE SOUTHERN WASHINGTON/NORTHERN AND
CENTRAL OREGON COAST TONIGHT.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KPQR 211634
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
833 AM PST SAT NOV 21 2009
.SYNOPSIS...A WARM FRONT WILL APPROACH THE OREGON COAST THIS
AFTERNOON THEN PUSH INLAND THIS EVENING. A COLD FRONT WILL QUICKLY
FOLLOW TONIGHT AS A SURFACE LOW PRESSURE SYSTEM MOVES INLAND NEAR THE
WA OREGON BORDER. A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUN
AFTERNOON AND NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES MON.
&&
.SHORT TERM...LATEST MODEL RUNS CONTINUE TO EXHIBIT DIFFERENCES IN
TRACK OF THE SURFACE LOW COMING IN TONIGHT. UPPER FEATURES APPEAR
PRETTY WELL AGREED ON...WITH A STRONG SHORTWAVE MOVING ACROSS THE
FORECAST AREA TONIGHT...DIGGING TO THE ESE. GIVEN THE TRACT OF THE
UPPER VORT MAX AND THE NEGATIVE TILT OF THE UPPER TROUGH...CONTINUE
TO PREFER A MORE SOUTHERLY TRACK OF THE SURFACE LOW...AS SUCH PREFER
THE 00Z RUN OF THE ECMWF WHICH TAKES A SURFACE LOW E ROUGHLY ACROSS
KKLS AT 12Z SUN. TIMING OF THE COLD FRONT IN ALL MODELS INDICATES
FRONTAL PASSAGE ON THE COAST NOT UNTIL SOMETIME TONIGHT. GIVEN THE
CONTINUED UNCERTAINTIES IN THE MODELS...FOR NOW WILL LEAVE HEADLINE
AS A HIGH WIND WATCH FOR THE N AND CENTRAL OREGON COAST...BUT LIMIT
IT TO TONIGHT PERIOD. WINDS INLAND LOOK GUSTY WITH AND BEHIND THE
FRONT AS THERE ARE STRONG PRESSURE RISES BEHIND THE FRONT. AT THIS
TIME THOUGH...BEST GUESS IS FOR WINDS TO BE BELOW WARNING
CRITERIA...ALTHOUGH WILLAMETTE VALLEY MAY APPROACH ADVISORY LEVELS
LATE TONIGHT.
DOPPLER RADAR CONTINUES TO SHOW SHOWERS SPREADING OVER MOST OF THE
FORECAST AREA THIS MORNING AS WESTERLY FLOW ALOFT FOLLOWS THE UPPER
TROUGH. WITH UPPER RIDGING LATER TODAY...AND LOW LEVEL FLOW BACKING
MORE TO THE S...SHOULD SEE SHOWERS DROP OFF TODAY. OVERNIGHT SNOWFALL
AMOUNTS IN THE CASCADES SINCE LAST EVENING HAVE RANGED FROM ROUGHLY 4
TO 9 INCHES. FOR NOW WILL HANG ONTO THE SNOW ADVISORY FOR THE N
OREGON AND S WA CASCADES TODAY...ALTHOUGH WILL LIKELY SEE A
SIGNIFICANT DROPOFF IN SNOWFALL LATER THIS MORNING. WILL CONTINUE
THE WINTER STORM WARNING FOR THE CASCADES AS MOISTURE...STRENGTH OF
THE FRONT AND THE POST FRONTAL FLOW ALL FAVOR SIGNIFICANT SNOWFALL
LATER TONIGHT AND SUN.
CURRENT MODEL RUNS INDICATE BEST CHANCES FOR PRECIPITATION MONDAY
WILL SHIFT N INTO WA WITH WARM FRONT OVERRUNNING. THE UPPER RIDGE
HOLDS COLD FRONT AT BAY UNTIL MON NIGHT. LIKENS
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...WEAK HIGH PRES
BUILDS OVER THE FORECAST AREA MON NIGHT. MODELS SHOW A WEAK SYSTEM
APPROACH THE COAST EARLY TUE...BUT IT TRACKS FURTHER NORTH AND
LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF THE CWA. THIS RIDGE IS
MORE PERSISTENT THAN PREVIOUS MODEL RUNS SUGGESTED. IT MANAGES TO
DELAY THE ARRIVAL OF A SECOND SYSTEM THROUGH THUR. BY MID NEXT
WEEK...MODELS DISAGREE ON THE SOLUTION FOR THE WEEKEND. GFS MODEL
RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK ON PRECIP THROUGH THURS
NIGHT BUT THE CURRENT RUN SHOWS RAIN EXTENDING TO THE CASCADES THURS
NIGHT. SO FAR...MODELS SUGGEST A FAIRLY NICE WEEKEND AS ANOTHER UPPER
HIGH PRES TEMPORARILY SETS UP OVER THE PAC NW. LRAMIREZ
&&
.AVIATION...LITTLE CHANGE IN OVERALL CONDITIONS THIS MORNING.
PREDOMINATELY VFR WITH SCATTERED SHOWERS...WHICH MAY BRING VERY
BRIEF MVFR CIGS. CONDITIONS REMAIN VFR THROUGH TODAY...THOUGH WILL
SEE INCREASING MVFR ALONG THE COAST AFTER 20Z AS WARM FRONT SWINGS
ACROSS THE REGION. COLD FRONT TONIGHT WILL BRING INCREASING MVFR
AFTER 04Z...AND INCREASING SOUTHERLY WINDS.
KPDX AND APPROACHES...VFR CONDITIONS THROUGH 05Z...THEN INCREASING
MVFR CIGS AS COLD FRONT APPROACHES. WATCH FOR POTENTIAL OF LOW LEVEL
WIND SHEAR BETWEEN 00Z AND 06Z TONIGHT AS WILL SEE INCREASING SOUTH
WINDS ALOFT...BLOWING OVER THE LOW LEVEL EASTERLY FLOW COMING FROM
GORGE.ROCKEY/WOLFE
&&
.MARINE...NOT MUCH CHANGE. CONDITIONS WILL DETERIORATE LATER TODAY
AS WARM FRONT LIFTS ACROSS THE REGION. THIS WILL BRING GALE FORCE
SOUTH WINDS. HOWEVER...STRONG WINDS ARRIVE TONIGHT AS RATHER STRONG
LOW PRES PASSES ACROSS THE N OREGON COASTAL WATERS. STORM WARNING
FOR THE COASTAL WATERS FOR TONIGHT. WINDS TURN MORE W TO NW ON
SUNDAY AND BEGIN EASING. SEAS TONIGHT LIKELY TO PEAK IN THE 20 TO 25
FT RANGE...BUT WILL DROP QUICKLY ON SUN.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR THIS AFTERNOON.
STORM WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR TONIGHT.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS
THROUGH SUN.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES THROUGH 4 PM.
WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
CASCADES TONIGHT AND SUNDAY.
HIGH WIND WATCH FOR THE NORTHERN AND CENTRAL OREGON COAST
TONIGHT.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KSEW 211233 AAA
AFDSEW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
433 AM PST SAT NOV 21 2009
UPDATED THE AVIATION AND MARINE SEGMENTS.
.SYNOPSIS...A WEAK RIDGE WILL MOVE THROUGH WESTERN WASHINGTON THIS
MORNING...FOLLOWED QUICKLY BY A VIGOROUS FRONTAL SYSTEM. THIS SYSTEM
WILL BRING RAIN AND WINDY CONDITIONS TONIGHT AND SUNDAY. HEAVY SNOW
WILL FALL IN THE MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW
3000 FEET. A WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND
MONDAY NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATE IN THE WEEK.
&&
.SHORT TERM...WE HAVE NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON
BETWEEN AN UPPER TROUGH THAT MOVED THROUGH THE AREA OVERNIGHT AND A
WEAK UPPER RIDGE OFFSHORE ALONG 130W. THERE ARE STILL SCATTERED
SHOWERS ACROSS THE FORECAST AREA THIS MORNING...AND A PUGET SOUND
CONVERGENCE ZONE EXTENDING ACROSS ISLAND AND SNOHOMISH COUNTIES. IT
IS STILL BREEZY IN SOME AREAS...BUT THE WIND SHOULD EASE OVER THE
NEXT FEW HOURS AS THE SURFACE HIGH PRESSURE THAT HAS BEEN BUILDING
INTO THE AREA SHIFTS EAST OF THE CASCADES AHEAD OF THE NEXT FRONT.
THE FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT AND TEMPERATURES
ACROSS THE WESTERN WASHINGTON LOWLANDS WERE IN THE UPPER 30S TO MID
40S AT 3 AM.
THE WEAK RIDGE OFFSHORE WILL MOVE QUICKLY ACROSS WESTERN WASHINGTON
THIS MORNING...AND THE CONVERGENCE ZONE WILL LIKELY WEAKEN AND
DISSIPATE. THE SOUTH END OF AN OCCLUDED FRONT SWINGING INTO BRITISH
COLUMBIA WILL QUICKLY FOLLOW THE RIDGE...WITH SIGNIFICANT
PRECIPITATION REACHING THE COAST AND OLYMPICS THIS AFTERNOON. A
FRONTAL WAVE BEGINNING TO DEVELOP NEAR 45N/145W WILL DEEPEN AS IT
MOVES RAPIDLY EASTWARD WITH THE HELP OF A 140 KT JET. IT WILL MOVE
THROUGH THE FORECAST AREA TONIGHT.
HEAVY SNOW IN THE MOUNTAINS LOOKS LIKE A SURE BET. THE SNOW LEVEL
WILL RISE ONLY TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...AND
PRECIPITATION AMOUNTS WILL BE IMPRESSIVE. LIQUID AMOUNTS OF 3 TO 4
INCHES IN THE OLYMPICS ARE POSSIBLE THROUGH SUNDAY MORNING --
TRANSLATING ROUGHLY TO 30 TO 40 INCHES OF SNOW. EVEN THE RELATIVELY
DRIER HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS. WATER
EQUIVALENTS IN THE CASCADES WILL LIKELY BE IN THE 1 TO 3 INCH
RANGE...FOR SNOWFALL TOTALS OF 10 INCHES TO 2.5 FT. THE WINTER STORM
WATCH WILL BE UPGRADED TO A WARNING WITH THE EARLY MORNING FORECAST
PACKAGE.
ONE MATTER THAT IS SOMEWHAT UNCERTAIN IS THE TRACK OF THE SURFACE
LOW. THE MOST LIKELY SCENARIO IS THAT IT WILL REACH THE CENTRAL
WASHINGTON COAST AROUND MIDNIGHT TONIGHT...TRACK NORTHEAST ACROSS
THE OLYMPIC PENINSULA AND THE NORTH PART OF THE PUGET SOUND REGION
TO AROUND MT BAKER AT 4 AM...THEN HEAD RAPIDLY INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS...BUT THERE
APPEARS TO BE LITTLE THREAT OF A WIND STORM.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON AND EVENING...
AND AN UPPER RIDGE WILL MOVE INLAND SUNDAY NIGHT. THE RIDGE WILL
QUICKLY HEAD EAST OF THE CASCADES MONDAY AND ANOTHER FRONTAL SYSTEM
JUST UPSTREAM OF THE RIDGE WILL ARRIVE. THIS SYSTEM COULD INITIALLY
BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT IT WILL WEAKEN AS IT MOVES INLAND
MONDAY NIGHT. BY RECENT STANDARDS THIS WILL BE AN UNEVENTFUL SYSTEM
AND IT WILL MARK THE BEGINNING OF A PERIOD OF QUIETER...THOUGH NOT
NECESSARILY DRY...WEATHER. MCDONNAL
.LONG TERM...A WEAK UPPER RIDGE WILL FOLLOW THE FRONT THAT MOVES
THROUGH MONDAY AND MONDAY NIGHT. THERE IS JUST A CHANCE OF RAIN IN
THE FORECAST FOR TUESDAY AND WEDNESDAY...WITH A FAIRLY GOOD CHANCE
FOR SOME DRY WEATHER OVER THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY
MOVE ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER
FRONTAL WAVE WILL PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND
FRIDAY...THOUGH DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY
BY LATE IN THE WEEK. MCDONNAL
&&
.HYDROLOGY...THE SYSTEM COMING IN TODAY THROUGH MIDDAY SUNDAY ...
WHILE IT WILL PRODUCE IMPRESSIVE AMOUNTS OF PRECIPITATION...WILL
HAVE MINIMAL EFFECT ON RIVERS EXCEPT POSSIBLY FOR THE TWO RIVERS
THAT ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND
THE LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. WITH THE
SNOW LEVEL ONLY RISING TO AROUND 3000 FT...IT WILL BE A MOUNTAIN
SNOW PRODUCER NOT A FLOODING RAIN PRODUCER.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
TODAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM
#2 INTO THE NORTH FORK SKOKOMISH RIVER TODAY. THIS RELEASE WILL KEEP
THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR THE RIVER
TO REMAIN JUST BELOW FLOOD STAGE TONIGHT AND SUNDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT IS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. MCDONNAL
&&
.AVIATION...A WEAK...UPPER RIDGE OVER THE REGION WILL MOVE E
TONIGHT...ALLOWING A STRONG...UPPER TROF TO MOVE OVER THE AREA.
INCREASING WLY FLOW ALOFT...SUBSIDING AND BECOMING NW LATE TONIGHT.
AT THE SFC...A FRONTAL SYSTEM OVER THE ERN PAC WILL RAPIDLY APPROACH
WRN WA DURING THE DAY TODAY...RESULTING IN INCREASED SLY WINDS. THE
OCCLUDED FRONT WILL MOVE ACROSS THE AREA THIS EVENING. A SECONDARY
SFC LOW IS ANTICIPATED TO DEVELOP OFF THE FAR SW WA OR FAR NW OREGON
COAST THIS EVENING...AND TRACK NEWD ACROSS THE AREA LATER TONIGHT.
THUS EXPECT THE WINDS TO BACK BEHIND THE OCCLUDED FRONT THIS
EVENING...AND THIS SHOULD RAISE THE POTENTIAL FOR LLWS SINCE WINDS
ABOVE THE SFC WILL REMAIN SLY. WINDS WILL PICK UP DRAMATICALLY FROM
THE W OR SW LATE TONIGHT OR EARLY SUNDAY ONCE THE SFC LOW MOVES E OF
THE AREA.
MEANWHILE...A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WAS ROUGHLY
LOCATED BETWEEN KPAE AND KAWO AT THIS TIME. THIS FEATURE SHOULD
DRIFT N AND DISSIPATE BY MIDMORNING AS ITS SUPPORT WANES.
KSEA...WINDS WILL REMAIN SLY TODAY...BECOMING MORE ELY TONIGHT.
THERE WILL BE A POTENTIAL FOR LLWS BETWEEN 0000 AND 1200 UTC SUNDAY
DUE TO ELY WINDS AT THE SFC AND STRONG SLY WINDS NEAR 2K FT. HAVE
HELD OFF ON MENTIONING THIS IN THE TAF TIL WE SEE ANOTHER MODEL RUN.
THE CURRENT MODEL SOLUTIONS WERE QUITE DIFFERENT THAN THE PREVIOUS
RUN DUE TO A MORE VIGOROUS SYSTEM NOW EXPECTED TO AFFECT THE AREA.
WINDS WILL INCREASE DRAMATICALLY FROM THE SW SOMETIME BETWEEN 1000
UTC AND 1200 UTC SUNDAY. CONCERNING CIGS...ANTICIPATE CIGS TO
GRADUALLY LOWER DURING THE DAY...ALTHOUGH THERE WILL BE OCCASIONAL
CIGS NEAR 2500 FT THIS MORNING. BY LATE THIS EVENING...CIGS SHOULD
BE NEAR 2K FT...WITH RAIN AND FOG REDUCING VSBYS INTO THE 3-5SM
RANGE.
&&
.MARINE...THERE WAS A SIGNIFICANT CHANGE IN THE FORECAST FROM THE
PREVIOUS ONE DUE TO A MORE VIGOROUS SYSTEM EXPECTED TO AFFECT THE
AREA TODAY. SLY WINDS ARE STILL ANTICIPATED TO INCREASE DURING THE
DAY...AHEAD OF A FAST-MOVING FRONTAL SYSTEM STILL WELL OFFSHORE...
FOR GALE OR SMALL CRAFT ADVISORY WIND SPEEDS. THE OCCLUDED FRONT
WILL SWEEP ACROSS THE AREA THIS EVENING. DUE TO SOMEWHAT LOW
CONFIDENCE HAVE WENT WITH A SMALL CRAFT ADVISORY FOR THE NORTHERN
INLAND WATERS AND EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA TODAY
INSTEAD OF UPGRADING THE PREVIOUS GALE WATCH TO A WARNING.
ANOTHER SURFACE WAVE OR LOW IS EXPECTED TO DEVELOP OFF THE FAR SW
WASHINGTON OR FAR NW OREGON COAST TONIGHT...AND THIS WILL CAUSE THE
WINDS TO BACK AND DROP OFF...ESPECIALLY ACROSS THE INLAND WATERS.
THE LOW WILL MOVE NE ACROSS INTERIOR WESTERN WASHINGTON OVERNIGHT.
WINDS WILL KICK BACK UP LATE TONIGHT OR EARLY SUNDAY IN RESPONSE TO
STRONG ONSHORE OR WESTERLY FLOW DEVELOPING. CONFIDENCE WAS FAIRLY
HIGH THAT GALE FORCE WINDS WILL DEVELOP OVER THE STRAIT OF JUAN DE
FUCA EARLY SUNDAY...THUS HAVE ISSUED A GALE WATCH FOR THE CENTRAL
AND EASTERN STRAIT. THERE IS A POSSIBILITY THAT WINDS MAY BRIEFLY
REACH STORM FORCE...NEAR 50 KNOTS...OVER THE CENTRAL STRAIT SUNDAY
MORNING WITH THE INITIAL PUSH.
ANTICIPATE THE ONSHORE FLOW TO WEAKEN AND BECOME SOUTHERLY SUNDAY
NIGHT. THE NEXT FRONTAL SYSTEM WILL AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR A
PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THROUGH THIS
EVENING.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING
WATERS.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT TIL NOON MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 211212
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PDT SAT NOV 21 2009
.SYNOPSIS...A WEAK RIDGE WILL MOVE THROUGH WESTERN WASHINGTON THIS
MORNING...FOLLOWED QUICKLY BY A VIGOROUS FRONTAL SYSTEM. THIS SYSTEM
WILL BRING RAIN AND WINDY CONDITIONS TONIGHT AND SUNDAY. HEAVY SNOW
WILL FALL IN THE MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW
3000 FEET. A WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND
MONDAY NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATE IN THE WEEK.
&&
.SHORT TERM...WE HAVE NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON
BETWEEN AN UPPER TROUGH THAT MOVED THROUGH THE AREA OVERNIGHT AND A
WEAK UPPER RIDGE OFFSHORE ALONG 130W. THERE ARE STILL SCATTERED
SHOWERS ACROSS THE FORECAST AREA THIS MORNING...AND A PUGET SOUND
CONVERGENCE ZONE EXTENDING ACROSS ISLAND AND SNOHOMISH COUNTIES. IT
IS STILL BREEZY IN SOME AREAS...BUT THE WIND SHOULD EASE OVER THE
NEXT FEW HOURS AS THE SURFACE HIGH PRESSURE THAT HAS BEEN BUILDING
INTO THE AREA SHIFTS EAST OF THE CASCADES AHEAD OF THE NEXT FRONT.
THE FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT AND TEMPERATURES
ACROSS THE WESTERN WASHINGTON LOWLANDS WERE IN THE UPPER 30S TO MID
40S AT 3 AM.
THE WEAK RIDGE OFFSHORE WILL MOVE QUICKLY ACROSS WESTERN WASHINGTON
THIS MORNING...AND THE CONVERGENCE ZONE WILL LIKELY WEAKEN AND
DISSIPATE. THE SOUTH END OF AN OCCLUDED FRONT SWINGING INTO BRITISH
COLUMBIA WILL QUICKLY FOLLOW THE RIDGE...WITH SIGNIFICANT
PRECIPITATION REACHING THE COAST AND OLYMPICS THIS AFTERNOON. A
FRONTAL WAVE BEGINNING TO DEVELOP NEAR 45N/145W WILL DEEPEN AS IT
MOVES RAPIDLY EASTWARD WITH THE HELP OF A 140 KT JET. IT WILL MOVE
THROUGH THE FORECAST AREA TONIGHT.
HEAVY SNOW IN THE MOUNTAINS LOOKS LIKE A SURE BET. THE SNOW LEVEL
WILL RISE ONLY TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...AND
PRECIPITATION AMOUNTS WILL BE IMPRESSIVE. LIQUID AMOUNTS OF 3 TO 4
INCHES IN THE OLYMPICS ARE POSSIBLE THROUGH SUNDAY MORNING --
TRANSLATING ROUGHLY TO 30 TO 40 INCHES OF SNOW. EVEN THE RELATIVELY
DRIER HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS. WATER
EQUIVALENTS IN THE CASCADES WILL LIKELY BE IN THE 1 TO 3 INCH
RANGE...FOR SNOWFALL TOTALS OF 10 INCHES TO 2.5 FT. THE WINTER STORM
WATCH WILL BE UPGRADED TO A WARNING WITH THE EARLY MORNING FORECAST
PACKAGE.
ONE MATTER THAT IS SOMEWHAT UNCERTAIN IS THE TRACK OF THE SURFACE
LOW. THE MOST LIKELY SCENARIO IS THAT IT WILL REACH THE CENTRAL
WASHINGTON COAST AROUND MIDNIGHT TONIGHT...TRACK NORTHEAST ACROSS
THE OLYMPIC PENINSULA AND THE NORTH PART OF THE PUGET SOUND REGION
TO AROUND MT BAKER AT 4 AM...THEN HEAD RAPIDLY INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS...BUT THERE
APPEARS TO BE LITTLE THREAT OF A WIND STORM.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON AND EVENING...
AND AN UPPER RIDGE WILL MOVE INLAND SUNDAY NIGHT. THE RIDGE WILL
QUICKLY HEAD EAST OF THE CASCADES MONDAY AND ANOTHER FRONTAL SYSTEM
JUST UPSTREAM OF THE RIDGE WILL ARRIVE. THIS SYSTEM COULD INITIALLY
BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT IT WILL WEAKEN AS IT MOVES INLAND
MONDAY NIGHT. BY RECENT STANDARDS THIS WILL BE AN UNEVENTFUL SYSTEM
AND IT WILL MARK THE BEGINNING OF A PERIOD OF QUIETER...THOUGH NOT
NECESSARILY DRY...WEATHER. MCDONNAL
.LONG TERM...A WEAK UPPER RIDGE WILL FOLLOW THE FRONT THAT MOVES
THROUGH MONDAY AND MONDAY NIGHT. THERE IS JUST A CHANCE OF RAIN IN
THE FORECAST FOR TUESDAY AND WEDNESDAY...WITH A FAIRLY GOOD CHANCE
FOR SOME DRY WEATHER OVER THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY
MOVE ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER
FRONTAL WAVE WILL PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND
FRIDAY...THOUGH DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY
BY LATE IN THE WEEK. MCDONNAL
&&
.HYDROLOGY...THE SYSTEM COMING IN TODAY THROUGH MIDDAY SUNDAY ...
WHILE IT WILL PRODUCE IMPRESSIVE AMOUNTS OF PRECIPITATION...WILL
HAVE MINIMAL EFFECT ON RIVERS EXCEPT POSSIBLY FOR THE TWO RIVERS
THAT ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND
THE LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. WITH THE
SNOW LEVEL ONLY RISING TO AROUND 3000 FT...IT WILL BE A MOUNTAIN
SNOW PRODUCER NOT A FLOODING RAIN PRODUCER.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
TODAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM
#2 INTO THE NORTH FORK SKOKOMISH RIVER TODAY. THIS RELEASE WILL KEEP
THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR THE RIVER
TO REMAIN JUST BELOW FLOOD STAGE TONIGHT AND SUNDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT IS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. MCDONNAL
&&
.AVIATION...DELAYED.
&&
.MARINE...A STRONG FRONTAL SYSTEM WILL APPROACH THE AREA TODAY...
RESULTING IN INCREASED SOUTHERLY FLOW. THE OCCLUDED FRONT WILL THEN
MOVE ACROSS THE AREA THIS EVENING. STRONG ONSHORE OR WESTERLY FLOW
WILL DEVELOP ON SUNDAY IN THE WAKE OF THIS FRONT. EXPECT THE NEXT
FRONTAL SYSTEM TO AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR A
PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THROUGH THIS
EVENING.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING
WATERS.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT TIL NOON MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 211132
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
330 AM PST SAT NOV 21 2009
.SYNOPSIS...
AFTER A SHORT RELATIVELY QUIET BREAK IN THE WEATHER TODAY...A
STRONGER AND COLDER STORM SYSTEM WILL BRING THE POTENTIAL FOR
MODERATE TO HEAVY SNOWFALL OVER MUCH OF THE REGION TONIGHT AND
SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO PASS THROUGH
THE INLAND NORTHWEST EVERY 24 TO 36 HOURS THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...
TODAY...WHILE THIS MORNING`S SATELLITE LOOP LOOKS MESSY...IN GENERAL
THE FORECAST AREA IS CURRENTLY UNDER AN INTER TROUGH COLD POOL
ALOFT WHICH WILL EXIT THE REGION AND ALLOW A DIRTY AND WEAK SHORT
WAVE RIDGE TO SET UP OVER THE REGION FOR THIS AFTERNOON. IN THE
WAKE OF LAST EVENINGS COLD FRONT PASSAGE BREEZY WINDS WILL
CONTINUE THROUGH THE MORNING AS A COOLER AIR MASS FILLS THE BASIN.
THERE WILL LIKELY BE SOME RESIDUAL SNOW SHOWERS MAINLY
CONCENTRATED OVER THE IDAHO PANHANDLE MOUNTAINS AND NEAR THE
CASCADE CREST...WITH PLENTY OF CLOUDS AND A SMALL CHANCE OF A
STRAY VALLEY RAIN OR SNOW SHOWER POSSIBLE OVER THE RISING TERRAIN
OF THE EASTERN BASIN TODAY AS A MOIST WESTERLY FLOW ALOFT
CONTINUES. HIGH TEMPERATURES TODAY WILL HAVE TROUBLE BREAKING OUT
OF THE UPPER THIRTIES AT MOST LOCATIONS OTHER THAN THE LOWEST
VALLEYS.
TONIGHT THROUGH SUNDAY...A VERY TRICKY FORECAST FOR THE NEXT 24 TO
36 HOURS. THE NEXT STORM SYSTEM...VISIBLE ON PACIFIC SATELLITE AS
A DEVELOPING BAROCLINIC LEAF STRUCTURE APPROACHING 140W THIS
MORNING...WILL MOVE ASHORE SOMETIME THIS EVENING AND CROSS THE
FORECAST AREA OVERNIGHT AND INTO SUNDAY MORNING. THERE ARE SOME
SIGNIFICANT MODEL DIFFERENCES WITH THE TRACK OF THE DEVELOPING SURFACE
LOW AND THE STRENGTH OF THE PARENT TROUGH. ALL THE MODELS DEVELOP
A STRONG SURFACE LOW JUST OFF THE COAST THIS AFTERNOON AND EJECT
IT INLAND TONIGHT. THE GFS AND CANADIAN MODELS TRACK THE LOW
THROUGH THE CENTRAL CASCADES AND SWING IT NORTH INTO BRITISH
COLUMBIA...WHILE THE ECMWF AND NAM GUIDANCE TRACK THE LOW THROUGH
THE SOUTHERN COLUMBIA BASIN. THIS LOW TRACK IS CRITICAL FOR SNOW
AMOUNT POTENTIAL. ALTHOUGH ALL MODELS INDICATE SIGNIFICANT
ACCUMULATING SNOW IS LIKELY OVERNIGHT SATURDAY AND SUNDAY
MORNING...A MORE SOUTHERLY TRACK WILL BRING HEAVIER SNOW AMOUNTS
TO THE VALLEYS AND BASIN. THUS CONFIDENCE IS HIGH THAT MOST OF THE
FORECAST AREA NORTH OF INTERSTATE 90 WILL EXPERIENCE AT LEAST A
COUPLE INCHES OF SNOW TONIGHT AND SUNDAY MORNING...WITH MODERATE
TO HEAVY ACCUMULATIONS IN THE MOUNTAINS. CONFIDENCE IS LOW AT
THIS TIME WHICH MODEL WILL VERIFY BEST...AND THUS UNCERTAINTY
REMAINS ABOUT THE POTENTIAL FOR HIGHLIGHTS WITH THIS SYSTEM. THUS
A SLEW OF WATCHES HAVE BEEN ISSUED...AND HOPEFULLY FURTHER MODEL
RUNS TODAY WILL SETTLE ON A CONFIDENT SOLUTION. AT THIS TIME WE
HAVE OPTED FOR A TRACK THAT IS SLIGHTLY SOUTH OF THE GFS/CANADIAN
MODELS AND DELAYED THE TIMING CLOSER TO THE EC/NAM GIVEN THE
SATELLITE EXTRAPOLATION AND AGGRESSIVE DIGGING OF THE PARENT
TROUGH. THIS ARGUES FOR AN ONSET OF LIGHT TO MODERATE SNOW IN THE
WESTERN ZONES THIS EVENING...INTENSIFYING OVERNIGHT THEN CUTTING
OUT/TAPERING OFF WITH THE COLD FRONT PASSAGE SUNDAY MORNING. ONSET
OVER THE EAST AND NORTHERN ZONES WILL HOLD OFF UNTIL LATE
OVERNIGHT SATURDAY OR EARLY SUNDAY MORNING...REACH MAXIMUM
INTENSITY SUNDAY MORNING AND TAPER OFF SUNDAY AFTERNOON WITH THE
USUAL LINGERING DENSE SNOW SHOWERS OVER THE IDAHO PANHANDLE. /FUGAZZI
SUNDAY NIGHT THROUGH FRIDAY...THE WEEKEND STORM SYSTEM CONTINUES
ITS EXIT TO THE EAST SUNDAY NIGHT ALLOWING FOR THE HIGHER POPS
ASSOCIATED WITH IT TO SHOW A SIMILAR EXIT OUT TO THE EAST SUNDAY
NIGHT AS WEAK RIDGING MOVES THROUGH BEHIND IT. THIS RIDGING IS NOT
WELL AMPLIFIED AND APPEARS PRONE TO OVERTOPPING BY TWO STORM
SYSTEMS. THE FIRST STORM SYSTEM DRAGS A WELL MAINTAINED MOISTURE
TAPS THROUGH EASTERN WASHINGTON AND NORTHERN IDAHO MONDAY NIGHT
INTO TUESDAY WHICH DEFLATES THE WEAK RIDGING FURTHER. THIS ALLOW
THE SECOND STORM SYSTEM TO EXERT SOME INFLUENCE AS EARLY AS LATE
IN THE DAY TUESDAY...HOWEVER THE RIDGE APPEARS TO SLOWLY AMPLIFY
AS A FEW SHORTWAVES START TO DIG ON THE WEST SIDE/NORTHS SIDE OF
THE JET OF THE LARGE BAROCLINIC BAND/MOISTURE TAP ASSOCIATED WITH
THIS SECOND SYSTEM. THE RESULT IS A POSSIBLY SHUNTING OF ANY
PRECIP BAN FRONTAL FEATURE BACK UP TO THE NORTH AND WEST FROM
TUESDAY NIGHT TO AS LATE AS THANKSGIVING. EVENTUALLY A DIGGING
SHORTWAVE GETS ENOUGH SIGNIFICANT CYCLOGENESIS GOING ON THE
BAROCLINIC BAND OFFSHORE TO GET IT WRAPPED UP INTO A COMPACT LOW
THAT DUMBBELLS AROUND WITH ANOTHER LOW TO ITS NORTH AS IT MOVES
INLAND SOMETIME BETWEEN THE PERIOD BETWEEN THANKSGIVING AND
FRIDAY. /PELATTI
&&
.AVIATION...
BREEZY CONDITIONS IN THE WAKE OF A COLD FRONT PASSAGE LAST NIGHT
WILL KEEP GENERALLY VFR VISIBILITIES AT ALL TAF SITES THIS
MORNING...WITH SOME OCCASIONAL MVFR AND IFR STRATUS CEILINGS AT
KGEG/KSFF AND KCOE UNTIL 16Z. A WEAK RIDGE ALOFT WILL PROMOTE VFR
CONDITIONS AT ALL TAF SITES THROUGH 03Z TONIGHT...WITH LINGERING
SNOW SHOWERS LOCALLY OBSCURING MOUNTAINS IN THE IDAHO PANHANDLE. THE
NEXT PACIFIC STORM SYSTEM WILL SPREAD MVFR AND LOCAL IFR CIELINGS TO
THE WESTERN REACHES OF THE REGION AFTER 03Z TONIGHT...MAINLY
IMPACTING THE KEAT AND KMWH TAF SITES. CONDITIONS AT EASTERN TAF
SITES WILL BEGIN TO DETERIORATE BY THE END OF THE TAF PERIOD AT 12Z
SUNDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 39 32 37 27 39 31 / 20 70 90 10 40 10
COEUR D`ALENE 39 31 37 28 40 31 / 20 60 90 20 50 20
PULLMAN 40 32 36 28 42 32 / 20 60 90 20 40 20
LEWISTON 47 36 41 30 48 35 / 10 60 90 20 30 20
COLVILLE 39 33 40 28 38 30 / 30 100 90 10 60 20
SANDPOINT 33 32 37 28 36 30 / 40 90 90 20 60 30
KELLOGG 32 30 34 27 35 30 / 70 70 100 40 60 40
MOSES LAKE 45 32 43 26 43 30 / 10 80 50 0 40 10
WENATCHEE 43 32 43 29 41 33 / 30 90 50 10 50 10
OMAK 43 31 42 25 40 27 / 40 100 50 0 60 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
COEUR D`ALENE AREA.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING FOR
NORTHERN PANHANDLE.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY AFTERNOON
ABOVE 2500 FEET FOR CENTRAL PANHANDLE MOUNTAINS.
WA... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
SPOKANE AREA.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING FOR
EAST SLOPES NORTHERN CASCADES.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR NORTHEAST MOUNTAINS...OKANOGAN
HIGHLANDS.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR OKANOGAN VALLEY...UPPER COLUMBIA
BASIN...WATERVILLE PLATEAU.
&&
$$
000
FXUS66 KOTX 211040
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
240 AM PST SAT NOV 21 2009
.SYNOPSIS...
AFTER A SHORT RELATIVELY QUIET BREAK IN THE WEATHER TODAY...A
STRONGER AND COLDER STORM SYSTEM WILL BRING THE POTENTIAL FOR
MODERATE TO HEAVY SNOWFALL OVER MUCH OF THE REGION TONIGHT AND
SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO PASS THROUGH
THE INLAND NORTHWEST EVERY 24 TO 36 HOURS THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...
TODAY...WHILE THIS MORNING`S SATELLITE LOOP LOOKS MESSY...IN GENERAL
THE FORECAST AREA IS CURRENTLY UNDER AN INTER TROUGH COLD POOL
ALOFT WHICH WILL EXIT THE REGION AND ALLOW A DIRTY AND WEAK SHORT
WAVE RIDGE TO SET UP OVER THE REGION FOR THIS AFTERNOON. IN THE
WAKE OF LAST EVENINGS COLD FRONT PASSAGE BREEZY WINDS WILL
CONTINUE THROUGH THE MORNING AS A COOLER AIR MASS FILLS THE BASIN.
THERE WILL LIKELY BE SOME RESIDUAL SNOW SHOWERS MAINLY
CONCENTRATED OVER THE IDAHO PANHANDLE MOUNTAINS AND NEAR THE
CASCADE CREST...WITH PLENTY OF CLOUDS AND A SMALL CHANCE OF A
STRAY VALLEY RAIN OR SNOW SHOWER POSSIBLE OVER THE RISING TERRAIN
OF THE EASTERN BASIN TODAY AS A MOIST WESTERLY FLOW ALOFT
CONTINUES. HIGH TEMPERATURES TODAY WILL HAVE TROUBLE BREAKING OUT
OF THE UPPER THIRTIES AT MOST LOCATIONS OTHER THAN THE LOWEST
VALLEYS.
TONIGHT THROUGH SUNDAY...A VERY TRICKY FORECAST FOR THE NEXT 24 TO
36 HOURS. THE NEXT STORM SYSTEM...VISIBLE ON PACIFIC SATELLITE AS
A DEVELOPING BAROCLINIC LEAF STRUCTURE APPROACHING 140W THIS
MORNING...WILL MOVE ASHORE SOMETIME THIS EVENING AND CROSS THE
FORECAST AREA OVERNIGHT AND INTO SUNDAY MORNING. THERE ARE SOME
SIGNIFICANT MODEL DIFFERENCES WITH THE TRACK OF THE DEVELOPING SURFACE
LOW AND THE STRENGTH OF THE PARENT TROUGH. ALL THE MODELS DEVELOP
A STRONG SURFACE LOW JUST OFF THE COAST THIS AFTERNOON AND EJECT
IT INLAND TONIGHT. THE GFS AND CANADIAN MODELS TRACK THE LOW
THROUGH THE CENTRAL CASCADES AND SWING IT NORTH INTO BRITISH
COLUMBIA...WHILE THE ECMWF AND NAM GUIDANCE TRACK THE LOW THROUGH
THE SOUTHERN COLUMBIA BASIN. THIS LOW TRACK IS CRITICAL FOR SNOW
AMOUNT POTENTIAL. ALTHOUGH ALL MODELS INDICATE SIGNIFICANT
ACCUMULATING SNOW IS LIKELY OVERNIGHT SATURDAY AND SUNDAY
MORNING...A MORE SOUTHERLY TRACK WILL BRING HEAVIER SNOW AMOUNTS
TO THE VALLEYS AND BASIN. THUS CONFIDENCE IS HIGH THAT MOST OF THE
FORECAST AREA NORTH OF INTERSTATE 90 WILL EXPERIENCE AT LEAST A
COUPLE INCHES OF SNOW TONIGHT AND SUNDAY MORNING...WITH MODERATE
TO HEAVY ACCUMULATIONS IN THE MOUNTAINS. CONFIDENCE IS LOW AT
THIS TIME WHICH MODEL WILL VERIFY BEST...AND THUS UNCERTAINTY
REMAINS ABOUT THE POTENTIAL FOR HIGHLIGHTS WITH THIS SYSTEM. THUS
A SLEW OF WATCHES HAVE BEEN ISSUED...AND HOPEFULLY FURTHER MODEL
RUNS TODAY WILL SETTLE ON A CONFIDENT SOLUTION. AT THIS TIME WE
HAVE OPTED FOR A TRACK THAT IS SLIGHTLY SOUTH OF THE GFS/CANADIAN
MODELS AND DELAYED THE TIMING CLOSER TO THE EC/NAM GIVEN THE
SATELLITE EXTRAPOLATION AND AGGRESSIVE DIGGING OF THE PARENT
TROUGH. THIS ARGUES FOR AN ONSET OF LIGHT TO MODERATE SNOW IN THE
WESTERN ZONES THIS EVENING...INTENSIFYING OVERNIGHT THEN CUTTING
OUT/TAPERING OFF WITH THE COLD FRONT PASSAGE SUNDAY MORNING. ONSET
OVER THE EAST AND NORTHERN ZONES WILL HOLD OFF UNTIL LATE
OVERNIGHT SATURDAY OR EARLY SUNDAY MORNING...REACH MAXIMUM
INTENSITY SUNDAY MORNING AND TAPER OFF SUNDAY AFTERNOON WITH THE
USUAL LINGERING DENSE SNOW SHOWERS OVER THE IDAHO PANHANDLE. /FUGAZZI
SUNDAY NIGHT THROUGH FRIDAY...THE WEEKEND STORM SYSTEM CONTINUES
ITS EXIT TO THE EAST SUNDAY NIGHT ALLOWING FOR THE HIGHER POPS
ASSOCIATED WITH IT TO SHOW A SIMILAR EXIT OUT TO THE EAST SUNDAY
NIGHT AS WEAK RIDGING MOVES THROUGH BEHIND IT. THIS RIDGING IS NOT
WELL AMPLIFIED AND APPEARS PRONE TO OVERTOPPING BY TWO STORM
SYSTEMS. THE FIRST STORM SYSTEM DRAGS A WELL MAINTAINED MOISTURE
TAPS THROUGH EASTERN WASHINGTON AND NORTHERN IDAHO MONDAY NIGHT
INTO TUESDAY WHICH DEFLATES THE WEAK RIDGING FURTHER. THIS ALLOW
THE SECOND STORM SYSTEM TO EXERT SOME INFLUENCE AS EARLY AS LATE
IN THE DAY TUESDAY...HOWEVER THE RIDGE APPEARS TO SLOWLY AMPLIFY
AS A FEW SHORTWAVES START TO DIG ON THE WEST SIDE/NORTHS SIDE OF
THE JET OF THE LARGE BAROCLINIC BAND/MOISTURE TAP ASSOCIATED WITH
THIS SECOND SYSTEM. THE RESULT IS A POSSIBLY SHUNTING OF ANY
PRECIP BAN FRONTAL FEATURE BACK UP TO THE NORTH AND WEST FROM
TUESDAY NIGHT TO AS LATE AS THANKSGIVING. EVENTUALLY A DIGGING
SHORTWAVE GETS ENOUGH SIGNIFICANT CYCLOGENESIS GOING ON THE
BAROCLINIC BAND OFFSHORE TO GET IT WRAPPED UP INTO A COMPACT LOW
THAT DUMBBELLS AROUND WITH ANOTHER LOW TO ITS NORTH AS IT MOVES
INLAND SOMETIME BETWEEN THE PERIOD BETWEEN THANKSGIVING AND
FRIDAY. /PELATTI
&&
.AVIATION...
AREAS OF MVFR AND IFR CIGS WILL OCCUR THROUGH 18Z DUE TO ABUNDANT
LOW LEVEL MOISTURE ACROSS EASTERN WA/N IDAHO. IN THE LEE OF THE
CASCADES VFR CONDITIONS WILL PERSIST AT KEAT/KMWH AS DOWNSLOPE
FLOW HAS DRIED OUT THE LOWER LEVELS. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 39 32 37 27 39 31 / 20 70 90 10 40 10
COEUR D`ALENE 39 31 37 28 40 31 / 20 60 90 20 50 20
PULLMAN 40 32 36 28 42 32 / 20 60 90 20 40 20
LEWISTON 47 36 41 30 48 35 / 10 60 90 20 30 20
COLVILLE 39 33 40 28 38 30 / 30 100 90 10 60 20
SANDPOINT 33 32 37 28 36 30 / 40 90 90 20 60 30
KELLOGG 32 30 34 27 35 30 / 70 70 100 40 60 40
MOSES LAKE 45 32 43 26 43 30 / 10 80 50 0 40 10
WENATCHEE 43 32 43 29 41 33 / 30 90 50 10 50 10
OMAK 43 31 42 25 40 27 / 40 100 50 0 60 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
COEUR D`ALENE AREA.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING FOR
NORTHERN PANHANDLE.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY AFTERNOON
ABOVE 2500 FEET FOR CENTRAL PANHANDLE MOUNTAINS.
WA... WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
SPOKANE AREA.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING FOR
EAST SLOPES NORTHERN CASCADES.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR NORTHEAST MOUNTAINS...OKANOGAN
HIGHLANDS.
WINTER STORM WATCH FROM THIS EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR OKANOGAN VALLEY...UPPER COLUMBIA
BASIN...WATERVILLE PLATEAU.
&&
$$
000
FXUS66 KPQR 211019
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
220 AM PST SAT NOV 21 2009
.SYNOPSIS...A WARM FRONT WILL APPROACH THE OREGON COAST THIS
AFTERNOON THEN PUSH INLAND THIS EVENING. A COLD FRONT WILL QUICKLY
FOLLOW TONIGHT AS A SURFACE LOW PRESSURE SYSTEM MOVES INLAND NEAR
THE WA OREGON BORDER. A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUN
AFTERNOON AND NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES MON.
&&
.SHORT TERM...LATEST MODEL RUNS CONTINUE TO EXHIBIT DIFFERENCES IN
TRACK OF THE SURFACE LOW COMING IN TONIGHT. UPPER FEATURES APPEAR
PRETTY WELL AGREED ON...WITH A STRONG SHORTWAVE MOVING ACROSS THE
FORECAST AREA TONIGHT...DIGGING TO THE ESE. GIVEN THE TRACT OF THE
UPPER VORT MAX AND THE NEGATIVE TILT OF THE UPPER TROUGH...CONTINUE
TO PREFER A MORE SOUTHERLY TRACK OF THE SURFACE LOW...AS SUCH PREFER
THE 00Z RUN OF THE ECMWF WHICH TAKES A SURFACE LOW E ROUGHLY ACROSS
KKLS AT 12Z SUN. TIMING OF THE COLD FRONT IN ALL MODELS INDICATES
FRONTAL PASSAGE ON THE COAST NOT UNTIL SOMETIME TONIGHT. GIVEN THE
CONTINUED UNCERTAINIES IN THE MODELS...FOR NOW WILL LEAVE HEADLINE
AS A HIGH WIND WATCH FOR THE N AND CENTRAL OREGON COAST...BUT LIMIT
IT TO TONIGHT PERIOD. WINDS INLAND LOOK GUSTY WITH AND BEHIND THE
FRONT AS THERE ARE STRONG PRESSURE RISES BEHIND THE FRONT. AT THIS
TIME THOUGH...BEST GUESS IS FOR WINDS TO BE BELOW WARNING
CRITERIA...ALTHOUGH WILLAMETTE VALLEY MAY APPROACH ADVISORY LEVELS
LATE TONIGHT.
SHOWERS CONTINUE OVER MOST OF THE FORECAST AREA EARLY THIS MORNING
AS A WESTERLY FLOW ALOFT FOLLOWS THE UPPER TROUGH. WITH UPPER
RIDGING LATER TODAY...AND LOW LEVEL FLOW BACKING MORE TO THE
S...SHOULD SEE SHOWERS DROP OFF TODAY. OVERNIGHT SNOWFALL AMOUNTS IN
THE CASCADES SINCE LAST EVENING HAVE RANGED FROM ROUGHLY 4 TO 9
INCHES. FOR NOW WILL HANG ONTO THE SNOW ADVISORY FOR THE N OREGON
AND S WA CASCADES TODAY...ALTHOUGH WILL LIKELY SEE A SIGNIFICANT
DROPOFF IN SNOWFALL LATER THIS MORNING. WILL UPGRADE THE WATCH
TONIGHT TO A WARNING FOR THE CASCADES AS MOISTURE...STRENGTH OF THE
FRONT AND THE POST FRONTAL FLOW ALL FAVOR SIGNIFICANT SNOWFALL LATER
TONIGHT AND SUN.
WILL BACK OFF ON POPS FOR SUN NIGHT AND MON AS CURRENT MODEL RUNS
INDICATE BEST CHANCES FOR PRECIPITATION WILL SHIFT N INTO WA WITH
BEST WARM FRONT OVERRUNNING...AND THE UPPER RIDGE HOLDS COLD FRONT
AT BAY UNTIL MON NIGHT.
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
WEAK HIGH PRES BUILDS OVER THE FORECAST AREA MON NIGHT. MODELS SHOW
A WEAK SYSTEM APPROACH THE COAST EARLY TUE...BUT IT TRACKS FURTHER
NORTH AND LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF THE CWA. THIS
RIDGE IS MORE PERSISTENT THAN PREVIOUS MODEL RUNS SUGGESTED. IT
MANAGES TO DELAY THE ARRIVAL OF A SECOND SYSTEM THROUGH THUR. BY MID
NEXT WEEK...MODELS DISAGREE ON THE SOLUTION FOR THE WEEKEND. GFS
MODEL RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK ON PRECIP
THROUGH THURS NIGHT BUT THE CURRENT RUN SHOWS RAIN EXTENDING TO THE
CASCADES THURS NIGHT. SO FAR...MODELS SUGGEST A FAIRLY NICE WEEKEND
AS ANOTHER UPPER HIGH PRES TEMPORARILY SETS UP OVER THE PAC NW.
LRAMIREZ
&&
.AVIATION...LITTLE CHANGE IN OVERALL CONDITIONS THIS MORNING.
PREDOMINATELY VFR WITH SCATTERED SHOWERS...WHICH MAY BRING VERY
BRIEF MVFR CIGS. CONDITIONS REMAIN VFR THROUGH TODAY...THOUGH WILL
SEE INCREASING MVFR ALONG THE COAST AFTER 20Z AS WARM FRONT SWINGS
ACROSS THE REGION. COLD FRONT TONIGHT WILL BRING INCREASING MVFR
AFTER 04Z...AND INCREASING SOUTHERLY WINDS.
KPDX AND APPROACHES...VFR CONDITIONS THROUGH 05Z...THEN INCREASING
MVFR CIGS AS COLD FRONT APPROACHES. WATCH FOR POTENTIAL OF LOW LEVEL
WIND SHEAR BETWEEN 00Z AND 06Z TONIGHT AS WILL SEE INCREASING SOUTH
WINDS ALOFT...BLOWING OVER THE LOW LEVEL EASTERLY FLOW COMING FROM
GORGE. ROCKEY.
&&
.MARINE...NOT MUCH CHANGE. CONDITIONS WILL DETERIORATE LATER TODAY
AS WARM FRONT LIFTS ACROSS THE REGION. THIS WILL BRING GALE FORCE
SOUTH WINDS. HOWEVER...STRONG WINDS ARRIVE TONIGHT AS RATHER STRONG
LOW PRES PASSES ACROSS THE N OREGON COASTAL WATERS. WILL HOIST STORM
WARNING FOR THE COASTAL WATERS FOR TONIGHT. WINDS TURN MORE W TO NW
ON SUNDAY AND BEGIN EASING. SEAS TONIGHT LIKELY TO PEAK IN THE 20 TO
25 FT RANGE...BUT WILL DROP QUICKLY ON SUN.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR THIS AFTERNOON.
STORM WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE FOR TONIGHT.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBAR BAR CONDITIONS
THROUGH SUN.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES THROUGH 4 PM.
WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
CASCADES TONIGHT AND SUNDAY.
HIGH WIND WATCH FOR THE NORTHERN AND CENTRAL OREGON COAST
TONIGHT.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KOTX 210643
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1043 PM PST FRI NOV 20 2009
.SYNOPSIS...
AFTER A SHORT BREAK IN THE WEATHER ON SATURDAY...A STRONGER AND
COLDER STORM SYSTEM WILL BRING THE POTENTIAL FOR MODERATE TO HEAVY
SNOWFALL MAINLY IN THE HIGH VALLEYS AND MOUNTAINS. A SERIES OF STORM
SYSTEMS WILL CONTINUE TO PASS THROUGH THE INLAND NORTHWEST EVERY
24 TO 36 HOURS WELL INTO NEXT WEEK.
&&
.DISCUSSION...
A STRONG PACIFIC SYSTEM IS EXPECTED TO IMPACT THE INLAND NORTHWEST
SATURDAY NIGHT INTO SUNDAY MORNING AND WINTER STORM WATCHES HAVE
BEEN POSTED FOR PARTS OF THE AREA. THERE CONTINUES TO BE
DISAGREEMENT FROM MODEL TO MODEL REGARDING THE TRACK AND STRENGTH
OF A SFC LOW AS IT PASSES ACROSS WASHINGTON. THE 00Z GFS MODEL IS
THE STRONGEST AND TRACKS THE LOW ALONG THE WA/BC BORDER...WHILE
THE NAM IS SLOWER AND TRACKS THE LOW FROM PORTLAND TOWARDS
PULLMAN. THE NEW 00Z CANADIAN SUPPORTS THE GFS...WHILE THE 00Z
ECMWF HAS NOT YET COME IN BUT PREVIOUS ECMWF SUPPORTED THE NAM.
DOING A MODEL INITIALIZATION OF THIS SYSTEM...THE GFS INITIALIZED
A LITTLE BIT DEEPER COMPARED TO THE 12 HR FCST FROM THE 12Z ECMWF
WHICH WAS SUPPORTED BY SHIP OBSERVATIONS. WATER VAPOR ALSO SHOWS
SOME DARKENING WITH THIS SYSTEM WITH THE LEFT EXIT PORTION OF A
JET STREAK AIDING IN INTENSIFICATION. BASED ON SATELLITE TRENDS
AND THAT THE CANADIAN BACKS UP THE GFS AND WITH THE GFS APPEARING
TO HAVE A GOOD INITIALIZATION...LEANED TOWARDS THE GFS. THE GFS
SHOWS DEEP MOISTURE AND LIFT AS A 992-995MB SFC LOW TRACKS
THROUGH THE AREA WITH QPF AMOUNTS OVER AN INCH ALONG THE CASCADE
CREST AND OVER A HALF INCH OVER THE NORTHERN HALF OF EASTERN WA/N
IDAHO. THIS LOOKS TO FALL MOSTLY IN A 12 HOUR PERIOD WITH THE BULK
OF THE PRECIPITATION FALLING SATURDAY NIGHT IN THE CASCADES AND
OVERNIGHT SATURDAY INTO SUNDAY MORNING OVER EASTERN WA/N IDAHO.
TRICKY PART IS SNOW LEVELS WITH 1000-850MB THICKNESSES 1305-1310
DM...AND 850MB TEMPS OF -2 TO -3 SNOW LEVELS LOOK TO BE NEAR 2000
FEET. THUS THE WINTER STORM WATCHES HAVE BEEN ISSUED ABOVE THIS
ELEVATION. SNOW LEVELS COULD END UP A LITTLE HIGHER AT TIMES OVER
THE SPOKANE/COEUR D`ALENE AREA AS WELL AS THE PALOUSE WITH
SOUTHERLY LOW LEVEL WINDS DEVELOPING AS THE LOW TRACKS NORTH OF
THE AREA. THUS WITH LOWER CONFIDENCE IN THESE AREAS HELD OFF ON
ANY POTENTIAL WATCHES.
FOR TONIGHT DRIER AIR WILL CONTINUE TO MOVE INTO EASTERN
WASHINGTON BEHIND THE EARLIER COLD FRONT PASSAGE...WHILE UPSLOPE
POST FRONTAL SNOW SHOWERS FALL IN THE MOUNTAINS OF N IDAHO.
ACCUMULATIONS IN THE MOUNTAINS HOWEVER WILL ONLY RANGE FROM 1 TO 3
INCHES. JW
&&
.AVIATION...
AREAS OF MVFR AND IFR CIGS WILL OCCUR THROUGH 18Z DUE TO ABUNDANT
LOW LEVEL MOISTURE ACROSS EASTERN WA/N IDAHO. IN THE LEE OF THE
CASCADES VFR CONDITIONS WILL PERSIST AT KEAT/KMWH AS DOWNSLOPE
FLOW HAS DRIED OUT THE LOWER LEVELS. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 33 39 32 37 27 39 / 20 20 90 80 10 40
COEUR D`ALENE 33 39 31 37 28 40 / 40 20 80 70 20 50
PULLMAN 32 39 32 36 28 42 / 50 20 70 80 20 40
LEWISTON 36 47 36 41 30 48 / 40 10 40 90 20 30
COLVILLE 32 40 33 40 28 38 / 10 30 80 70 10 60
SANDPOINT 32 36 32 37 28 36 / 90 40 80 80 20 60
KELLOGG 32 33 30 34 27 35 / 90 70 90 90 40 60
MOSES LAKE 31 45 32 43 26 43 / 0 10 80 60 0 40
WENATCHEE 32 43 32 43 29 41 / 0 30 90 50 10 50
OMAK 28 43 31 42 25 40 / 10 60 90 60 0 60
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON ABOVE 2500 FEET FOR CENTRAL PANHANDLE MOUNTAINS.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING
FOR NORTHERN PANHANDLE.
WA...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING
FOR EAST SLOPES NORTHERN CASCADES.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR NORTHEAST MOUNTAINS...OKANOGAN
HIGHLANDS.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING
ABOVE 2000 FEET FOR OKANOGAN VALLEY...WATERVILLE PLATEAU.
&&
$$
000
FXUS66 KSEW 210515
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PST FRI NOV 20 2009
.SYNOPSIS...A TROUGH WILL MOVE THROUGH WESTERN WASHINGTON THIS
EVENING. A DEVELOPING SURFACE LOW IN THE EAST CENTRAL PACIFIC WILL
MOVE ACROSS SOUTHERN PORTIONS OF WASHINGTON SUNDAY NIGHT. A FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA MONDAY OR MONDAY NIGHT. YET
ANOTHER FRONT WILL MOVE ACROSS THE AREA MIDWEEK.
&&
.SHORT TERM...A RATHER STRONG ZONAL FLOW CONTINUES ACROSS THE
PACIFIC THIS EVENING. BUT THE PATTERN ACROSS NORTH AMERICA IS
INCREASINGLY SPLIT. SO WHILE INCOMING SYSTEMS OVER THE NEXT SEVERAL
DAYS WILL NOT LIKELY BE AS STRONG OR AS WET AS SYSTEMS THAT IMPACTED
THE AREA DURING THE LAST WEEK...THE TIMING AND PLACEMENT OF SYSTEMS
WILL BE INCREASINGLY DIFFICULT FOR NUMERICAL MODELS TO HANDLE AS
TIME MOVES FORWARD.
THIS EVENING A COLD UPPER TROUGH IS MOVING ACROSS THE AREA WITH 500
MB TEMPERATURES AROUND -33C AND 850 MB TEMPERATURES AROUND -3C. THE
AIR MASS IS RATHER UNSTABLE...BUT WITH ABUNDANT MOISTURE ALOFT THE
CAPE IS ONLY AROUND 300J/KG AND THE CAPE PROFILE IS SKINNY. AS THE
CENTER OF THE UPPER TROUGH MOVED ACROSS THE AREA AROUND 5 PM...QUITE
A FEW THUNDERSTORMS DEVELOPED ACROSS THE NORTHERN INLAND WATERS.
THESE HAVE SINCE DIED OUT AS THEY MOVED INTO THE CANADIAN COASTAL
RANGE. EARLIER...PRES GRADIENTS WERE STRONGLY SOUTHERLY AND NEAR
GALE FORCE SLY WINDS DEVELOPED ACROSS THE INLAND WATERS. NOW THAT
STRONG INFLOW HAS DEVELOPED IN THE STRAIT OF JUAN DE FUCA...THE SW
WINDS OVER THE INLAND VALLEYS WILL GRADUALLY DIE DOWN. AN AREA OF
CONVERGENCE IS CENTERED OVER SKAGIT COUNTY THIS EVENING. AS THE
UPPER TROUGH MOVES EAST AND FLOW BECOMES MORE WESTERLY AND RELAXES
SOMEWHAT...EXPECT A PUGET SOUND CONVERGENCE ZONE TO SET UP AROUND
THE EVERETT AREA AND CONTINUE NORTH OF THE SEATTLE AREA OVERNIGHT
BEFORE DISSIPATING. SNOW LEVELS IN THE MOUNTAINS SHOULD AVERAGE
AROUND 2000 FT AND HIGH END ADVISORY AMOUNTS OF SNOW ARE POSSIBLE IN
THE NORTH CASCADES NORTH OF STEVENS PASS IN SNOHOMISH AND SKAGIT
COUNTIES.
A DEVELOPING FRONTAL SYSTEM IS SEEN AHEAD OF A LEADING EDGE OF A 140
KT JET STREAK NEAR 44N/159W. THE 00Z NAM AND GFS SOLUTIONS ARE IN
AGREEMENT WITH THEIR 18Z RUNS IN DEVELOPING THIS WAVE TO ABOUT 990
MB AND SLAMMING IT INTO THE PAC NW SOMEWHERE BETWEEN THE MOUNT OF
THE COLUMBIA RIVER...NAM12...AND THE CHEHALIS GAP BEFORE TAKING IT
NE INTO THE CENTRAL TO NORTH CASCADES SAT NIGHT. MODERATELY STRONG
WINDS WITH MARINE GALES WILL ACCOMPANY THIS LOW...BUT WIND SPEEDS
AND DIRECTIONS WILL BE QUITE DEPENDENT ON THE UNCERTAIN TRACK OF
THIS FAST MOVING LOW. IF THERE WERE ANY COOL AIR AROUND OR HIGHER
PRES N AND EAST OF THE AREA...WE WOULD NEED TO WATCH OUT FOR LOWLAND
SNOW IN ADVANCE OF AND TO THE NORTH OF THE TRACK OF THE LOW WITH WET
BULB COOLING IN THE DEFORMATION ZONE TO THE NORTH. HOWEVER...ALL
MODELS SHOW TEMPERATURES BETWEEN 2000 FT AND THE SURFACE TO BE 2-4
DEG C TOO WARM...WHICH IS CONSISTENT WITH THE MARINE AIR MASS IN
PLACE AND THE SOMEWHAT SPLIT NATURE OF THIS NEXT INCOMING SYSTEM.
1.0 TO 1.5 INCHES OF PRECIPITATION ARE SEEN TO THE NORTH OF THE
TRACK OF THE LOW SAT NIGHT. WITH SNOW LEVELS AROUND 2000 FT AND
PRECIPITATION AMOUNTS OF THIS DEGREE...WILL ISSUE A WINTER STORM
WATCH FOR ALL OF THE MOUNTAINS SAT NIGHT THROUGH MIDDAY SUN.
CONDITIONS BRIEFLY DRY LATER SUN AFTERNOON INTO SUN NIGHT BETWEEN
SUN MORNINGS DEPARTING LOW AND THE NEXT FRONTAL SYSTEM THAT MOVES IN
MON OR MON NIGHT.
WILL UPDATE THE ZONES TO REFINE THE SHORT TERM AND TO ADD THE WINTER
STORM WATCH FOR THE MOUNTAINS SAT NIGHT THROUGH MIDDAY SUN. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...A WARM FRONT
MOVES THRU WRN WA MONDAY...AT 700MB THE TEMP WARMS FROM -14C LATE
SUN TO ARND -5C MON AFTERNOON. THE SURFACE PRES PATTERN IS RATHER
LACKLUSTER WITH THIS FRONT ON MONDAY...THE NAM SHOWS A FAIRLY DECENT
SE GRADIENT MONDAY MORNING BUT THEN BY MONDAY EVENING THE FRONT IS
DISSIPATING AND PRES IS RISING WITH LIGHT GRADIENTS AS 500MB HEIGHTS
RISE INTO THE LOWER 560S. THERE IS A GOOD CHANCE OF SOME DRY WEATHER
TUE AS THAT RIDGE BUILDS IN...THEN A FNTL BAND MOVES THRU WED OR
THU...OR BOTH. THE LATEST GFS SUGGESTS THE REMNANTS OF A WEAKENING
FNTL BAND FOR WED AND THEN A STRONGER SYS THU. THERE IS PRETTY GOOD
AGREEMENT THAT THE FIRST HALF OF THE WEEK WILL SEE A FAIRLY HIGH
FREEZING LEVEL BUT NOT MUCH PRECIP...AND THEN A LOWERING SNOW LEVEL
LATE IN THE WEEK WITH THE BEST GUESS FOR A DECENT COLD FROPA THU
NIGHT...SO FRIDAY COULD BE POSTFRONTAL AND COOL SHOWERY BUT I
HAVEN`T GONE FOR THAT MUCH DETAIL FOR A DAY SEVEN FCST THO I DID
SHOW THE SNOW LEVEL BACK BELOW THE PASSES BY FRIDAY FOR BETTER
SKIING LIKELY TOWARD THE END OF NEXT WEEK. 19
&&
.HYDROLOGY...PRECIPITATION HAS BECOME SHOWERY. WHILE 0.5-1.0 INCHES
OF PRECIPITATION ARE LIKELY IN THE NORTH CASCADES TONIGHT AND EARLY
SATURDAY...SNOW LEVELS WILL BE AROUND 2000 FT AND AFFECTS ON THE
RIVERS SHOULD BE MINIMAL.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
SATURDAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN
DAM #2 INTO THE NORTH FORK SKOKOMISH RIVER ON SATURDAY. THIS RELEASE
WILL KEEP THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR
THE RIVER TO REMAIN JUST BELOW FLOOD STAGE SATURDAY NIGHT AND SUNDAY.
THE SATSOP RIVER AT SATSOP HAS JUST FALLEN BELOW FLOOD STAGE AROUND
730 PM THIS EVENING. WILL LIKELY TAKE THE FLOOD WARNING FOR THE
SATSOP DOWN BY 10 PM.
THE LOWEST REACH OF THE CHEHALIS WILL BOUNCE AROUND AT A FOOT OR
LESS BELOW FLOOD STAGE THROUGH SATURDAY. MORE RAIN SATURDAY NIGHT
COULD KEEP THE THE LOWER CHEHALIS NEAR FLOOD STAGE. WILL MAINTAIN
THE FLOOD WATCH FOR THE CHEHALIS THROUGH SUNDAY FOR NOW. IF FLOODING
DOES OCCUR IT SHOULD BE MINOR.
ANOTHER SYSTEM WILL ARRIVE SATURDAY NIGHT INTO SUNDAY MORNING WITH
SIGNIFICANT PRECIPITATION IN THE MOUNTAINS. SNOW LEVELS WILL REMAIN
LOW THROUGH SUNDAY...AROUND 2000 FT...SO RENEWED FLOODING IS NOT
EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER.
ALBRECHT/BURKE
&&
.AVIATION...AN UPPER TROF OVER WRN WA WILL CONTINUE MOVING E. BY
EARLY SATURDAY...THIS SYSTEM WILL BE OVER THE GREAT BASIN. A
WEAK...UPPER RIDGE WILL FOLLOW ON THE HEELS OF THE UPPER TROF.
CONTINUED WLY FLOW ALOFT. THE AIR MASS WILL REMAIN MOIST. SLIGHTLY
UNSTABLE ATMOSPHERE OVER THE AREA WILL BECOME STABLE OVERNIGHT.
AT THE SFC...STRONG ONSHORE FLOW WILL WEAKEN OVERNIGHT. ANOTHER
FRONTAL SYSTEM WILL APPROACH THE REGION DURING THE DAY SATURDAY FOR
INCREASED SLY FLOW. CIGS WILL GENERALLY BE IN THE 4-8K FT RANGE...
ALTHOUGH EXPECT AREAS OF CIGS NEAR 2K FT. THERE MAY BE SOME PATCHY
FOG...REDUCING VSBYS DOWN TO 3SM...LATER TONIGHT OR EARLY SATURDAY
MORNING OVER THE SW INTERIOR IF THERE IS SUFFICIENT CLEARING.
CONCERNING THE PUGET SOUND CONVERGENCE ZONE /PSCZ/...IT APPEARED
THAT THE PSCZ WAS DEVELOPING OVER ITS FAVORED POSITION...JUST N OF
THE KING/SNOHOMISH COUNTY BORDER WHERE IT WILL REMAIN STATIONARY.
WOULD NOT RULE OUT AN ISOLATED LIGHTNING STRIKE WITHIN THE PSCZ TIL
MIDNIGHT. THE PSCZ WILL DISSIPATE LATE TONIGHT AS THE FLOW BECOMES
UNFAVORABLE FOR MAINTAINING IT.
KSEA...CIGS WILL GENERALLY BE IN THE 5-8K FT RANGE OVERNIGHT BUT
EXPECT OCCASIONAL CIGS NEAR 2500 FT. SLY WINDS WILL DIMINISH
OVERNIGHT.
&&
.MARINE...STRONG WESTERLY FLOW WILL WEAKEN AND BECOME SOUTHERLY
OVERNIGHT. A FRONTAL SYSTEM WILL APPROACH THE AREA DURING THE DAY
SATURDAY... RESULTING IN INCREASED SOUTHERLY FLOW. THE COLD OR
OCCLUDED FRONT IS EXPECTED TO MOVE ACROSS THE AREA SATURDAY NIGHT.
ONSHORE FLOW WILL CONTINUE ON SUNDAY BETWEEN SYSTEMS. THE NEXT
FRONTAL SYSTEM WILL AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR
A PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES
TONIGHT.
.A WINTER STORM WATCH IS IN EFFECT FOR SATURDAY NIGHT THROUGH
MIDDAY SUNDAY IN THE OLYMPICS AND NORTH AND CENTRAL CASCADES
AND PASSES.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE CENTRAL AND
EASTERN STRAIT OF JUAN DE FUCA TIL MIDNIGHT.
.GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA SATURDAY
THROUGH SATURDAY EVENING.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE PUGET SOUND
AND HOOD CANAL TIL 4 AM SATURDAY.
.A GALE WATCH IS IN EFFECT FOR THE NORTHERN INLAND WATERS
FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING.
.A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR
CONDITIONS IS IN EFFECT TIL 10 AM SUNDAY.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KPQR 210410
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
809 PM PST FRI NOV 20 2009
.SYNOPSIS...RESIDUAL SHOWERS WILL CONTINUE THE REMAINDER OF THE NIGHT
AFTER THE PASSAGE OF A COLD FRONT. ANOTHER FRONT APPROACHES LATER
SATURDAY...WITH STRONG WINDS POSSIBLE ON THE COAST AND
SIGNIFICANT SNOW EXPECTED IN THE CASCADES. THE NEXT STORM ARRIVES
LATER MONDAY.
&&
.SHORT TERM...STILL CONSIDERABLE SHOWERS THIS EVENING...ESPECIALLY
ALONG THE CASCADES AND WILL KEEP THE ADVISORY FOR SNOW. A WARM FRONT
APPROACHES SATURDAY WITH INCREASING WINDS ALONG THE COAST CONSISTENT
WITH HIGH WIND WATCH.
THE TRAILING COLD FRONT GETS SLOWED BY A WAVE WITH ANOTHER LOW
DEVELOPING. THE LOWS PUSHES TO THE COAST SATURDAY NIGHT. ALL THE
MODELS HAVE VARIED SOLUTIONS...MANY OF WHICH WOULD RESULT IN
SIGNIFICANT WINDS IN THE INTERIOR AT FIRST LOOK. BUT...THE UPPER
TROUGH BECOMES NEGATIVELY TILTED...SOMEWHAT MORE IN THE NAM THAN THE
GFS...WITH MOMENTUM TRANSFERRING SOUTH. NOT GOOD FOR A STRONG
SOUTHERLY PUSH OF WINDS. ALSO THE SURFACE LOW IS FILLING AS IT MOVES
INLAND AND THE LOW IS NOT MOVING NORTH OR NORTH NORTHEASTWARD
ALLOWING THE STRONG UP VALLEY PUSH OF WINDS.
SO WILL WAIT TO SEE IF WE GET A BETTER AND MORE CONSISTENT LOOK ON
LATER RUNS ON DEALING WITH THE WINDS. WITH THAT SECOND WAVE SLOWING
THINGS DOWN...WILL EXPAND THE WINTER STORM WATCH TO COVER ALL DAY
SUNDAY IN THE CASCADES RATHER THAN JUST THE MORNING. SS
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...WEAK HIGH PRES
BUILDS OVER THE FORECAST AREA MON NIGHT.
MODELS SHOW A WEAK SYSTEM APPROACH THE COAST EARLY TUE...BUT IT
TRACKS FURTHER NORTH AND LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF
THE CWA. THIS RIDGE IS MORE PERSISTENT THAN PREVIOUS MODEL RUNS
SUGGESTED. IT MANAGES TO DELAY THE ARRIVAL OF A SECOND SYSTEM
THROUGH THUR. BY MID NEXT WEEK...MODELS DISAGREE ON THE SOLUTION FOR
THE WEEKEND. GFS MODEL RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK
ON PRECIP THROUGH THURS NIGHT BUT THE CURRENT RUN SHOWS RAIN
EXTENDING TO THE CASCADES THURS NIGHT. SO FAR...MODELS SUGGEST A
FAIRLY NICE WEEKEND AS ANOTHER UPPER HIGH PRES TEMPORARILY SETS UP
OVER THE PAC NW. LRAMIREZ
&&
.AVIATION...COOL SHOWERS CONTINUE TO STREAM IN OFF THE PACIFIC THIS
EVENING IN UNSTABLE WESTERLY FLOW. VFR CONDITIONS ARE EXPECTED
ACROSS ALL AREAS TONIGHT WITH A 40% CHANCE OF MVFR CONDITIONS IN AND
NEAR SHOWERS. A WARM FRONT WILL BRING RAIN AND MVFR CONDITIONS TO
THE COAST AND COAST RANGE BY MIDDAY SATURDAY.
KPDX AND APPROACHES...CONDITIONS ARE EXPECTED TO REMAIN PRIMARILY
VFR TONIGHT WITH A 40% CHANCE OF MVFR CONDITIONS IN AND NEAR
SHOWERS. VFR CONDITIONS ARE EXPECTED SATURDAY.
&&
.MARINE...SMALL CRAFT WINDS WILL CONTINUE THROUGH SATURDAY MORNING
BEFORE THE NEXT STRONGER FRONT BOOSTS GUSTS TO LOW END GALE CRITERIA
SATURDAY AFTERNOON WITH THE POSSIBILITY OF ANOTHER WAVE GENERATING
STRONG GALES AND POSSIBLY STORM FORCE WINDS BY LATE SATURDAY NIGHT
INTO SUNDAY MORNING. SEAS CURRENTLY HOVERING AROUND 12 FT AND SHOULD
BUILD TO 16 TO 18 BY SATURDAY NIGHT.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
THROUGH SAT EVENING.
SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO
FLORENCE THROUGH SAT MORNING.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO
FLORENCE THROUGH SAT MORNING.
GALE WARNING CAPE SHOALWATER TO CASCADE HEAD SAT MORNING
THROUGH LATE SATURDAY NIGHT.
GALE WARNING CASCADE HEAD TO FLORENCE SAT MORNING THROUGH
SATURDAY EVENING.
STORM WATCH CASCADE HEAD TO FLORENCE SAT EVENING THROUGH
SUNDAY MORNING.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES THROUGH SAT MORNING.
WINTER WEATHER WATCH FOR SNOW FOR THE SOUTH WASHINGTON AND
NORTH OREGON CASCADES AND THE CASCADES IN LANE COUNTY FOR
SATURDAY AFTERNOON THROUGH SUNDAY.
HIGH WIND WATCH FOR THE NORTHERN AND CENTRAL OREGON COAST
FOR SAT AFTERNOON AND NIGHT.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KOTX 210330
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
730 PM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION THIS EVENING AND BRING
LIGHT VALLEY RAIN AND MOUNTAIN SNOW TO THE REGION. AFTER A SHORT
BREAK IN THE WEATHER ON SATURDAY...A STRONGER AND COLDER STORM
SYSTEM WILL BRING THE POTENTIAL FOR MODERATE MOUNTAIN AND VALLEY
SNOW ACCUMULATIONS SATURDAY NIGHT AND INTO SUNDAY. A SERIES OF
STORM SYSTEMS WILL CONTINUE TO PASS THROUGH THE INLAND NORTHWEST
EVERY 24 TO 36 HOURS WELL INTO NEXT WEEK.
&&
.DISCUSSION...
MINOR UPDATE TO THE FORECAST FOR THE REST OF TONIGHT CONCERNING
PRECIPITATION CHANCES. COLD FRONT AS OF 7 PM WAS LOCATED NEAR THE
WASHINGTON/IDAHO BORDER WHERE A BAND OF STEADY RAIN AND MOUNTAIN
SNOW EXISTS. BEHIND THE FRONT DOWNSLOPE WESTERLY FLOW OFF THE
CASCADES HAS ENDED THE PRECIPITATION AT OMAK AND MOSES LAKE WITH
THE BACK EDGE OF THE PRECIPITATION OVER WESTERN SPOKANE AND
WHITMAN COUNTIES. AS THE FRONT CONTINUES TO MOVE EAST TONIGHT
AREAS WHERE RAIN HAS NOT YET DEVELOPED OVER SE WA/N IDAHO WILL
SOON SEE PRECIP DEVELOP TO AS THE FRONT CONTINUES TO MOVE EAST.
THUS...POPS OF 80-100 PCT REMAIN IN THE FCST FOR THE REST OF
TONIGHT IN THESE AREAS. CURRENT FORECAST LOOKS GOOD...BUT WILL
LIKELY UPDATE LATER TO LOWER POPS OVER FAR EASTERN WASHINGTON AS
THE FRONT EXITS THE AREA. JW
&&
.AVIATION...
FROM PREVIOUS DISCUSSION...A COLD FRONT WILL MOVE ACROSS THE FORECAST
THIS EVENING AND BE EAST OF THE AREA LATER TONIGHT. CONDITIONS
WILL BE MAINLY VFR WITH LOCALIZED AND BRIEF MVFR CEILINGS DURING
THE HEAVIEST PRECIPITATION. CONDITIONS WILL DRY OUT FROM THE WEST
BEHIND THE COLD FRONT AND EXPECT ENOUGH WIND TO KEEP THE LOWER
ATMOSPHERE MIXED ENOUGH FOR ONLY ISOLATED STRATUS DEVELOPMENT
SATURDAY MORNING. AFTER 16Z SATURDAY...SOUTHWEST WINDS WILL
INCREASE WITH GUSTS 20 TO 25 KTS. PRECIPITATION WILL AFFECT THE
WESTERN TAF SITES AFTER 18Z. /EK
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 33 39 32 37 27 39 / 80 20 90 80 10 40
COEUR D`ALENE 33 39 31 37 28 40 / 100 20 80 70 20 50
PULLMAN 32 39 32 36 28 42 / 90 20 70 80 20 40
LEWISTON 36 47 36 41 30 48 / 70 10 40 90 20 30
COLVILLE 32 40 33 40 28 38 / 80 30 80 50 10 60
SANDPOINT 32 36 32 37 28 36 / 90 40 80 60 20 60
KELLOGG 32 33 30 34 27 35 / 90 70 90 90 40 60
MOSES LAKE 31 45 32 43 26 43 / 10 10 80 60 0 40
WENATCHEE 32 43 32 43 29 41 / 0 30 90 50 10 50
OMAK 28 43 31 42 25 40 / 10 60 90 60 0 60
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KOTX 202345
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
345 PM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION THIS EVENING AND BRING
LIGHT VALLEY RAIN AND MOUNTAIN SNOW TO THE REGION. AFTER A SHORT
BREAK IN THE WEATHER ON SATURDAY...A STRONGER AND COLDER STORM
SYSTEM WILL BRING THE POTENTIAL FOR MODERATE MOUNTAIN AND VALLEY
SNOW ACCUMULATIONS SATURDAY NIGHT AND INTO SUNDAY. A SERIES OF
STORM SYSTEMS WILL CONTINUE TO PASS THROUGH THE INLAND NORTHWEST
EVERY 24 TO 36 HOURS WELL INTO NEXT WEEK.
&&
.DISCUSSION...
TONIGHT AND SATURDAY...THE SATELLITE LOOP IS SHOWING A TROUGH DIGGING
SOUTH ALONG THE WASHINGTON COAST. THE 12Z RUN OF THE MODELS WERE
VERY SIMILAR SHOWING THE COLD FRONT ON THE CASCADES AROUND 18Z
AND WEAKENING AS IT MOVED THROUGH THE FORECAST AREA BY 06Z THIS
EVENING. AT 21Z PRECIPITATION HAD BEEN FALLING ALONG THE CASCADE
CREST FOR SEVERAL HOURS WHILE KELN JUST REPORTED RAIN...IN
ADDITION SURFACE PRESSURE WAS STILL FALLING ALONG THE EAST SLOPES
OF THE CASCADES. THIS PUTS THE TIMING OF THE FRONT 3-4 HOURS
SLOWER THAN PREVIOUS THINKING DUE MAINLY TO THE 150KT JET DIGGING
THE LOW AND SLOWING EASTWARD PROGRESSION. FOR LATE THIS AFTERNOON
AND EARLY EVENING...PRECIPITATION WILL MOVE ACROSS THE FORECAST AREA
IN THE WARM SECTOR AHEAD OF THE COLD FRONT AND POPS WERE ADJUSTED
ACCORDINGLY. UP-GLIDE ALONG THE 285-295 ISENTROPIC SURFACE IS
IMPRESSIVE BUT THE STRETCHING FRONT HAS CUT-OFF THE MOISTURE TAP
FROM OUT IN THE PACIFIC. IN ADDITION LOCAL SOUNDINGS ARE INDICATING
A VERY DRY SUB- CLOUD LAYER AND ACROSS THE EASTERN ZONES SOUTHERLY
WINDS HAVE DRIED OUT THE LOWER ATMOSPHERE FURTHER. WHILE JUST
ABOUT ALL LOCATIONS WILL PICK UP MEASURABLE PRECIPITATION WITH THE
FRONT IT WILL TAKE A WHILE TO SATURATE THE LOWER ATMOSPHERE AND
PRECIPITATION WILL BE LOWERED. THE SOUTHERLY FLOW AHEAD OF THE
FRONT HAS KEPT SNOW LEVELS AT OR ABOVE 4000 FEET THROUGH EARLY
EVENING.
FOR THE REST OF TONIGHT EXPECT DRYING FROM THE WEST BEHIND THE
FRONT. SOUTHWEST WINDS WILL INCREASE RESULTING IN THE TYPICAL RAIN
SHADOW ALONG THE EAST SLOPES OF THE CASCADES AND PROMOTING UP-
SLOPING FLOW ACROSS THE EASTERN ZONES. SNOW LEVELS ARE EXPECTED
TO DROP BEHIND THE FRONT TO NEAR THE SURFACE. BUT BY THAT TIME RAIN AND
SNOW WILL TURN SHOWERY AND THE BEST CHANCES FOR MEASURABLE
PRECIPITATION WILL ALONG THE CASCADE CREST AND THE PANHANDLE
MOUNTAINS. SOUTHWEST WINDS WILL INCREASE TO BREEZY WITH GUSTS
OVERNIGHT 20-25 MPH ACROSS A LARGE PORTION OF THE FORECAST AREA.
THIS SHOULD KEEP FOG AND STRATUS FORMATION TO A MINIMUM.
SATURDAY WEAK AND FAST MOVING HIGH PRESSURE WILL BUILD IN BEHIND
THE COLD FRONT. WESTERLY FLOW INTO THE EASTERN MOUNTAINS WILL
KEEP OROGRAPHIC SHOWERS IN THE FORECAST FOR THOSE ZONES.
BY SATURDAY AFTERNOON THE NEXT STORM SYSTEM WILL BE KNOCKING ON
THE DOOR. SOUTHWEST FLOW WILL INCREASE WARM AIR ADVECTION AND
MOISTURE INTO THE NORTH WEST ZONES. THE 12Z AND NOW THE 18Z MODELS
ARE ALL PRETTY SIMILAR BRINGING IN A WEAK SHORT WAVE DISTURBANCE
THROUGH THE NORTHWEST ZONES BETWEEN 18-00Z SATURDAY AFTERNOON. THE
COMBINATION OF THE ISENTROPIC LIFT AND THE WAVE WILL BE ENOUGH TO
SUPPORT LIKELY OR BETTER POPS ACROSS THE NORTHWEST ZONES BY LATE
IN THE AFTERNOON. SNOW LEVELS WILL BE DOWN TO THE VALLEY FLOOR AND
1 TO 2 INCHES OF NEW SNOW WILL BE POSSIBLE BY LATE SATURDAY
AFTERNOON. TEMPERATURES WILL BE 5-7 DEGREES COOLER SATURDAY AND
VERY NEAR SEASONAL NORMALS. /TOBIN
...MOIST PACIFIC STORM TO BRING CHANCE FOR MODERATE SNOWS ABOVE
2000 FEET SATURDAY NIGHT THROUGH MIDDAY SUNDAY...
SATURDAY NT THROUGH SUNDAY NT...THE NEXT IN A LINE OF
MOIST PACIFIC STORMS WILL IMPACT THE REGION BRINGING RAIN AND SNOW
AS WELL AS MODERATE WINDS. MODEL GUIDANCE IS GENERALLY FAIR TO
POOR WITH THIS SYSTEM AND THIS IS MAKING FOR QUITE THE FORECAST
CHALLENGE TRYING TO SORT OUT THE DETAILS. LOOKING AT THE BIG
PICTURE...A MOIST 1.4" PWAT PLUME...COLD CORE SHORTWAVE
ENERGY...AND STRONG UPPER-LEVEL JET DYNAMICS ALL COME TOGETHER
TOMORROW AFTERNOON OFF THE WASHINGTON COAST RESULTING IN STRONG
CYCLOGENESIS WHICH WILL TRANSITION ACROSS THE PAC NW SATURDAY NT
THROUGH MIDDAY SUNDAY. MODELS ARE HAVING AN EXTREMELY DIFFICULT
TIME WITH THE DETAILS REGARDING THE STRENGTH OF THE LOW- LEVEL
CYCLOGENESIS AS WELL AS THE TRACK. THE TREND OFF THE NAM/GEM/ECMWF
HAS BEEN TOWARD A SOUTHERN TRACK WHICH BRINGS THE SFC CYCLONE
ALONG THE WA/OR BORDER AND HEAVIEST PRECIPITATION ACROSS THE
SOUTHERN COLUMBIA BASIN WHILE THE LAST FEW RUNS OF THE GFS
CONTINUE WITH MUCH DEEPER LOW (NEARLY 10MB DEEPER THAN OTHER
GUIDANCE) AND TRACK DIRECTLY ACROSS THE CWA WHICH WOULD RESULT IN
HEAVY PRECIPITATION ACROSS THE CENTRAL AND NORTHERN TIER ZONES. WITH
THE EC/NAM/GEM IN MUCH BETTER AGREEMENT AND SHOWING SOME
CONSISTENCY WITHIN THE LAST TWO RUNS...WILL LEAN IN THAT DIRECTION
AND PUT LESS WEIGHT WITH THE OUTLYING GFS.
STRONG ISENTROPIC ASCENT ALONG THE 280-295K SURFACE DEVELOPING
SATURDAY NIGHT WILL JUST ABOUT GUARANTEE PRECIPITATION FOR ALL
LOCATIONS...STARTING IN THE CASCADES AND NORTHERN MTNS FIRST THEN
SPREADING ACROSS THE BASIN AFTER A SHALLOW DRY LAYER LEFT IN THE
WAKE OF SATURDAY`S SYSTEM BECOMES MOISTENED. BUT IT WILL BE THE
PRECIPITATION SHIELD THAT DEVELOPS ALONG THE NORTHERN PERIPHERY OF
THE LOW-LEVEL CYCLONE...OR TROWAL AIRSTREAM WHICH BECOMES THE
FOCUS FOR THE HEAVIEST AMOUNTS AS THE CYCLONE TRACKS ACROSS THE
REGION. AGAIN...THE FORECAST HAS TRENDED TOWARD THE NAM/EC/GEM AND
POPS/QPF WERE REDUCED ALONG THE NORTHERN TIER AND INCREASED FOR
NEAR THE WA/OR BORDER. THE SECOND MAJOR CHALLENGE WILL BE SNOW
LEVELS. WITH SUCH A WARM MOIST TAP OF MOISTURE (NEARLY 0.50"
TONGUE NOSING INTO THE BASIN)...EXPECT SNOW LEVELS TO RISE WITHIN
THE 2000-3500K FT RANGE ALONG THE SOUTHERN BASIN TO 1500-2000K FT
LAYER ACROSS THE NORTH. THIS MAY LEAD TO ANOTHER EVENT WHERE SNOW
FALLS ACROSS THE WEST PLAINS INCLUDING THE SPOKANE AIRPORT WITH A
FEW INCHES BUT RAIN/SNOW MIX DOWNTOWN WITH LITTLE TO NO
ACCUMULATIONS. WITH CONFIDENCE GENERALLY POOR WITH THE STORM
TRACK...AND WHERE THE THE HEAVIEST PRECIPITATION BANDS WILL SET
UP...WILL LEAVE OUT EXACT SNOW AMTS IN THE AFD BUT POST
PRELIMINARY SNOW AMTS ON WEATHER STORY 2 LOCATED
(WEATHER.GOV/SPOKANE). BY LATE SUNDAY MORNING...THE SYSTEM BEGINS
TO WEAKEN AND TRACKS INTO CENTRAL IDAHO WITH STRONG WESTERLIES
RAPIDLY INCREASING AS STRONG COLD ADVECTION SLIDES DOWN THE
CASCADES. THIS WILL QUICKLY SHUT OFF THE PRECIPITATION FROM WEST
TO EAST AT THE EXPENSE OF STRONG WINDS DOWN THE EAST
SLOPES...WATERVILLE PLATEAU...AND WESTERN BASIN. WITH 850MB WINDS
INCREASING TO 40-55KTS...EXPECT WINDS IN LOCATIONS LIKE WENATCHEE
TO GUSTS IN EXCESS OF 35-40KTS. /SB
MONDAY THROUGH FRIDAY...THE REGION WILL BE AFFECTED BY A WEAK
FRONTAL SYSTEM ON MONDAY...FOLLOWED BY A DRYING RIDGE MIDWEEK. A
STRONGER SYSTEM WILL AFFECT THE FORECAST AREA ON THANKSGIVING DAY.
WARM FRONTAL PRECIPITATION WILL SPREAD ACROSS THE INLAND NORTHWEST
ON MONDAY. THERE ARE SOME DIFFERENCES IN THE TRACK OF THE SHORTWAVE
TROUGH BUT GENERALLY THE BEST FORCING REMAINS TO OUR NORTH. THIS
WILL KEEP THE BEST CHANCE OF PRECIPITATION ACROSS OUR NORTHERN ZONES.
PRECIPITATION IS EXPECTED TO BE EITHER RAIN OR A MIX OF RAIN AND
SNOW SOUTH OF I-90 WITH MAINLY SNOW TO THE NORTH. THE NORTHERN
VALLEYS AND THE WATERVILLE PLATEAU COULD SEE LIGHT SNOWFALL
ACCUMULATIONS BUT ANY SIGNIFICANT SNOWFALL WILL BE CONFINED TO THE
ELEVATIONS ABOVE 3500 FEET. AS THE COLD FRONT PUSHES THROUGH MONDAY
NIGHT THE FOCUS FOR PRECIPITATION WILL SHIFT TO THE EASTERN
MOUNTAINS AND BECOME MORE SHOWERY IN NATURE. ON TUESDAY A MID LEVEL
RIDGE WILL START TO BUILD OVER THE REGION. THERE IS SOME MOISTURE IN
THE WESTERLY FLOW ALOFT ALONG WITH SOME ISENTROPIC ASCENT ACROSS THE
NORTHERN TIER BUT ANY PRECIPITATION THAT OCCURS WILL BE LIGHT.
DAYTIME TEMPERATURES WILL BE ON A GRADUAL WARMING TREND THROUGH
MIDWEEK. BY WEDNESDAY NIGHT...CLEARING SKIES AND LIGHT WINDS WILL
ALLOW FOG AND LOW STRATUS FORMATION IN THE BASIN. EXPECT THIS WILL
SPREAD NORTH TO THE NORTHEAST VALLEYS NOT AFFECTED BY CLOUDS
LINGERING ALONG THE BC BORDER.
...THANKSGIVING DAY LOOKS TO BE WET BUT NOT WHITE ACROSS THE INLAND
NORTHWEST...
A STRONGER PACIFIC WEATHER SYSTEM WILL AFFECT THE REGION BY
THANKSGIVING DAY. THIS SYSTEM HAS A NICE MOISTURE TAP WITH PWATS
AROUND 150 PERCENT OF NORMAL. WE COULD SEE A GOOD SHOT OF
PRECIPITATION BUT LOW LEVEL SOUTHERLY FLOW WILL HAVE PUSHED SNOW
LEVELS ABOVE MOST VALLEY FLOORS. BY THURSDAY NIGHT THE COLD FRONT
SWINGS THROUGH AND SNOW LEVELS WILL DROP OVERNIGHT. BY THIS TIME
MOST OF THE PRECIPITATION WILL HAVE MOVED EAST TO THE PANHANDLE
MOUNTAINS. TEMPERATURES WILL RETURN TO NEAR SEASONAL NORMALS. /KELCH
&&
.AVIATION...
A COLD FRONT WILL MOVE ACROSS THE FORECAST THIS EVENING AND BE
EAST OF THE AREA LATER TONIGHT. CONDITIONS WILL BE MAINLY VFR
WITH LOCALIZED AND BRIEF MVFR CEILINGS DURING THE HEAVIEST
PRECIPITATION. CONDITIONS WILL DRY OUT FROM THE WEST BEHIND THE
COLD FRONT AND EXPECT ENOUGH WIND TO KEEP THE LOWER ATMOSPHERE
MIXED ENOUGH FOR ONLY ISOLATED STRATUS DEVELOPMENT SATURDAY
MORNING. AFTER 16Z SATURDAY...SOUTHWEST WINDS WILL INCREASE WITH
GUSTS 20 TO 25 KTS. PRECIPITATION WILL AFFECT THE WESTERN TAF
SITES AFTER 18Z. /EK
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 33 39 32 37 27 39 / 70 20 90 80 10 40
COEUR D`ALENE 33 39 31 37 28 40 / 80 20 80 70 20 50
PULLMAN 32 39 32 36 28 42 / 80 20 70 80 20 40
LEWISTON 36 47 36 41 30 48 / 70 10 40 90 20 30
COLVILLE 32 40 33 40 28 38 / 80 30 80 50 10 60
SANDPOINT 32 36 32 37 28 36 / 80 40 80 60 20 60
KELLOGG 32 33 30 34 27 35 / 90 70 90 90 40 60
MOSES LAKE 31 45 32 43 26 43 / 20 10 80 60 0 40
WENATCHEE 32 43 32 43 29 41 / 0 30 90 50 10 50
OMAK 28 43 31 42 25 40 / 20 60 90 60 0 60
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KSEW 202323
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI NOV 20 2009
.SYNOPSIS...A TROUGH WILL MOVE THROUGH WESTERN WASHINGTON THIS
EVENING. A FRONTAL SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON
SATURDAY AFTERNOON AND NIGHT. A WARM FRONT WILL REACH THE AREA
MONDAY. A RIDGE WILL BUILD OVER THE REGION TUESDAY. A FRONTAL SYSTEM
WILL MOVE SLOWLY THROUGH THE AREA LATER WEDNESDAY AND THURSDAY.
&&
.SHORT TERM...SFC AND UPPER TROF WILL MOVE THRU WRN WA THIS
EVENING...BLUSTERY ON THE COAST AS THE SFC TROF MOVED THRU THIS
AFTERNOON. BREEZY THIS EVENING IN THE INTERIOR AS WELL AS SFC PRES
GRADIENTS INCREASE AS THE TROF MOVES INLAND AND FILLS...AT 3PM
OLM-BLI GRADIENT HAD JUMPED TO +3.3MB AND THAT GRADIENT SHUD PEAK AT
+4.5 LATE THIS AFTERNOON...WINDY FOR A FEW HOURS TIL THE PSCZ SETS
UP AND WINDS WILL DECREASE...ESPECIALLY NORTH OF SEATTLE IN THE
PSCZ. WLY WINDS DVLPG AND INCREASING IN THE STRAIT W/ A WLY GALE IN
THE FCST TO AID THAT PSCZ. COOLER AIR ALOFT WILL DESTABILIZE THE AIR
MASS AND SHOWERS WILL MOVE THRU WRN WA...BECMG INCREASINGLY
OROGRAPHIC OVERNIGHT WITH A GOOD CHANCE OF A PSCZ SETTING UP. WINTER
WEATHER ADVISORY IN THE CASCADES...IF THE PSCZ SETS UP MIGHT SEE A
FOOT OF NEW SNOW FROM PILCHUCK TO INDEX AND UP TOWARD STEVENS PASS
OVERNIGHT. SNOW LEVEL DROPS FM 2500 TO 1500FT...XCP MIGHT BE ARND
1000FT BY MIDNIGHT IN THE PSCZ OVR THE CASCADES AS 700MB TEMP COOLS
TO -15C. A BIT OF A BREAK SATURDAY MORNING ALTHOUGH THE NAM KEEPS IT
PRETTY DRIPPY SO HAVE HIGHER POPS THAN I WOULD NORMALLY SHOW AHEAD
OF THE NEXT FRONT. THAT NEXT FRONTAL SYS AND SFC LOW PRES CENTERS IN
THE 18Z NAM ARE A MUCH BETTER MATCH TO THE GLOBAL MODELS. A FIRST
LOW CENTER WITH THE OCFNT REACHES NRN VANCOUVER ISLAND SATURDAY
EVENING...THE FRONT EXTENDS SOUTH ALONG THE WA AND ORE COAST...AND
THEN THE NAM SPINS UP A SECONDARY LOW TO 988MB WHICH REACHES THE NRN
OREGON COAST AFTER MIDNIGHT...WITH A TRACK THRU NW ORE BY DAYBREAK
SUN. THIS SYSTEM WILL BE COOLER THAN PREVIOUS SYSTEMS BUT LOW LEVEL
THICKNESS VALUES DO NOT SUPPORT TAKING THE SNOW LEVEL FCST MUCH BLO
1500FT. THE 18Z GFS IS A NOTCH FURTHER NORTH WITH THE SFC LOW PRES
TRACK WITH A 995MB CENTER REACHING LONG BEACH OR GRAYS HARBOR BY
10PM SAT...IT WILL BE WORTH TAKING A CLOSE LOOK AT THE 00Z MESOSCALE
MODELS...THE GFS TRACK COULD BE WINDY IF IT IS SIMILAR TO THE 18Z
RUN...AND THE MESO MODELS ARE OFTEN A NOTCH DEEPER. IN ANY EVENT
WITH BREEZY SOLUTIONS THERE WILL BE ENUF ONSHORE FLOW TO ENSURE THE
SNOW LEVEL DOESN`T DROP BLO MUCH 1500FT LATE SAT NITE. 19
.LONG TERM...A WARM FRONT MOVES THRU WRN WA MONDAY...AT 700MB THE
TEMP WARMS FROM -14C LATE SUN TO ARND -5C MON AFTERNOON. THE SURFACE
PRES PATTERN IS RATHER LACKLUSTER WITH THIS FRONT ON MONDAY...THE
NAM SHOWS A FAIRLY DECENT SE GRADIENT MONDAY MORNING BUT THEN BY
MONDAY EVENING THE FRONT IS DISSIPATING AND PRES IS RISING WITH
LIGHT GRADIENTS AS 500MB HEIGHTS RISE INTO THE LOWER 560S. THERE IS
A GOOD CHANCE OF SOME DRY WEATHER TUE AS THAT RIDGE BUILDS IN...THEN
A FNTL BAND MOVES THRU WED OR THU...OR BOTH. THE LATEST GFS SUGGESTS
THE REMNANTS OF A WEAKENING FNTL BAND FOR WED AND THEN A STRONGER
SYS THU. THERE IS PRETTY GOOD AGREEMENT THAT THE FIRST HALF OF THE
WEEK WILL SEE A FAIRLY HIGH FREEZING LEVEL BUT NOT MUCH PRECIP...AND
THEN A LOWERING SNOW LEVEL LATE IN THE WEEK WITH THE BEST GUESS FOR
A DECENT COLD FROPA THU NIGHT...SO FRIDAY COULD BE POSTFRONTAL AND
COOL SHOWERY BUT I HAVEN`T GONE FOR THAT MUCH DETAIL FOR A DAY SEVEN
FCST THO I DID SHOW THE SNOW LEVEL BACK BELOW THE PASSES BY FRIDAY
FOR BETTER SKIING LIKELY TOWARD THE END OF NEXT WEEK. 19
&&
.HYDROLOGY...IN THE OLYMPICS ALL THAT REMAINS IS FOR THE HEAVY RAIN
FROM LAST NIGHT TO DRAIN TO THE OCEAN. ALL RIVERS ARE FALLING AND
ONLY TWO ARE ABOVE FLOOD STAGE...THE SATSOP AND SKOKOMISH. ALLOWED
THE AREAL FLOOD WARNING FOR JEFFERSON AND CLALLAM COUNTIES TO EXPIRE
AT 230 PM.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
SATURDAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN
DAM #2 INTO THE NORTH FORK SKOKOMISH RIVER ON SATURDAY. THIS RELEASE
WILL KEEP THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR
THE RIVER TO REMAIN JUST BELOW FLOOD STAGE SATURDAY NIGHT AND SUNDAY.
THE LOWEST REACH OF THE CHEHALIS WILL BOUNCE AROUND AT A FOOT OR
LESS BELOW FLOOD STAGE THROUGH SATURDAY. MORE RAIN SATURDAY NIGHT
COULD KEEP THE THE LOWER CHEHALIS NEAR FLOOD STAGE...SO HAVE
EXTENDED THE WATCH THROUGH SUNDAY. EVEN LOCAL INFLOW FROM THE WEAK
SYSTEM ON SATURDAY NIGHT COULD CAUSE THE LOWER CHEHALIS TO APPROACH
FLOOD STAGE...BUT ANY FLOODING WILL BE MINOR.
THE CASCADES RECEIVED A BURST OF RAIN AS THE FRONT PASSED THIS
MORNING. THE NOOKSACK DRAINAGE RECEIVED THE MOST RAIN AND THE
NOOKSACK RIVER ROSE SLIGHTLY...BUT IT APPEARS TO HAVE CRESTED AT ALL
GAUGES AND IS HEADING BACK DOWN...WELL BELOW FLOOD STAGE. OTHER
RIVERS COMING OUT OF THE NORTH AND CENTRAL CASCADES SHOWED SMALL
RISES AND ARE NOW RECEDING. ONE EXCEPTION IS THE UPPER SNOQUALMIE
AND TOLT RIVERS WHICH ARE STILL RISING. HOWEVER RAINFALL AMOUNTS
WERE NOT ENOUGH TO CAUSE ANY PROBLEMS AND THE RIVERS SHOULD HEAD
BACK DOWN SOON.
ANOTHER SYSTEM WILL ARRIVE SATURDAY WITH SIGNIFICANT PRECIPITATION
LATE SATURDAY INTO SATURDAY NIGHT. HOWEVER...THIS SYSTEM IS COLDER
WITH THE MAJORITY OF THE PRECIPITATION BEING SNOW OVER THE
MOUNTAINS. NEW FLOODING IS NOT EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. BURKE
&&
.AVIATION...AN UPPER TROUGH AXIS WILL MOVE ACROSS WRN WA EARLY THIS
EVENING. THE ATMOSPHERE WILL BE SLIGHTLY UNSTABLE TONIGHT WITH
SHOWERS...AND SLIGHT CHANCE OF ISOLATED THUNDERSTORMS UNTIL AROUND 5
PM. LOW LEVEL MIXING OVERNIGHT SHOULD LIMIT LOWER STRATUS FORMATION
WITH FOG NOT EXPECTED. CIGS WILL GENERALLY RUN VFR THROUGH SAT
MORNING. MODERATE TO STRONG WLY FLOW TONIGHT WILL BECOME STRONG SLY
FLOW ALOFT ON SAT AHEAD OF AN APPROACHING SURFACE LOW AND FRONT.
A PUGET SOUND CONVERGENCE ZONE IS EXPECTED TO FORM EARLY THIS
EVENING NORTH OF EVERETT...THEN SAG SWD TO NEAR THE KING/SNOHOMISH
LINE BY LATE THIS EVENING. THE CONVERGENCE ZONE SHOULD DISSIPATE
EARLY SAT MORNING AS THE FLOW DAMPENS AHEAD OF THE NEXT SYSTEM.
.KSEA...SW WIND 10-14 KT WITH GUSTS UP TO 25 KT OVERNIGHT. THE
CONVERGENCE ZONE MAY REACH AS FAR SOUTH AS NORTH SEATTLE BUT IS NOT
LIKELY TO REACH THE TERMINAL. DTM
.MARINE...STRONG ONSHORE FLOW WITH SW GRADIENTS WARRANT KEEPING
SMALL CRAFT ADVISORIES FOR THE WATERS THROUGH TONIGHT. WILL KEEP
STRONG GALES IN THE CENTRAL AND E STRAIT WITH A STRONG POST FRONTAL
WLY SURGE EXPECTED DOWN THE STRAIT THIS EVENING. WINDS SHOULD EASE A
BIT LATER TONIGHT...POSSIBLY BACK TO SMALL CRAFT BY EARLY SAT
MORNING.
THE NEXT SYSTEM TO AFFECT THE AREA ARRIVES MIDDAY SAT IN THE FORM OF
WARM FRONT TO LIFT ACROSS WRN WA. MODELS DIFFER CONSIDERABLY ON THE
TRAILING SURFACE LOW. ON MODEL SHOWS TWO STRONG SUB 990 MB LOWS
TRACKING INTO VANCOUVER ISLAND AND THE OTHER INTO N OREGON. ANOTHER
MODEL SHOWS ONE SUB 990 MB LOW GOING INTO KHQM ON THE S WA COAST.
THE EXACT TRACK HAS A HIGH IMPACT ON THE WIND SPEEDS SAT AFTERNOON
THROUGH SAT NIGHT. THERE DOES APPEAR TO BE A FAIRLY STRONG FRONT TO
STILL DRAG ACROSS...SO I WILL GO WITH A GALE WATCH FOR NOW AND LET
THE NEXT SHIFT TRY TO FIGURE OUT IF THE SURFACE LOW IS HEADING N OR
S OF WA OR RIGHT ACROSS.
SEAS WILL REMAIN HIGH THROUGH TONIGHT...AROUND 15 FT. ON SAT...SEAS
WILL SUBSIDE SLIGHTLY TO AROUND 12 FT BUT HAZARDOUS SEAS WILL
CONTINUE WITH ROUGH TO SEVERE BAR CONDITIONS. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES TNGT.
PZ...A GALE WARNING IS IN EFFECT FOR THE CENTRAL AND EAST STRAIT TIL
MIDNIGHT TONIGHT.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL REMAINING WATERS
THROUGH SAT MORNING.
.A SMALL CRAFT ADVISORY FOR SEVERE BAR CONDITIONS IS IN EFFECT
FOR THE GRAYS HARBOR BAR.
.A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS...EAST
STRAIT...AND NORTH INTERIOR FROM MIDDAY SAT THROUGH SAT
EVENING.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 202245
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
245 PM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION THIS EVENING AND BRING
LIGHT VALLEY RAIN AND MOUNTAIN SNOW TO THE REGION. AFTER A SHORT
BREAK IN THE WEATHER ON SATURDAY...A STRONGER AND COLDER STORM
SYSTEM WILL BRING THE POTENTIAL FOR MODERATE MOUNTAIN AND VALLEY
SNOW ACCUMULATIONS SATURDAY NIGHT AND INTO SUNDAY. A SERIES OF
STORM SYSTEMS WILL CONTINUE TO PASS THROUGH THE INLAND NORTHWEST
EVERY 24 TO 36 HOURS WELL INTO NEXT WEEK.
&&
.DISCUSSION...
TONIGHT AND SATURDAY...THE SATELLITE LOOP IS SHOWING A TROUGH DIGGING
SOUTH ALONG THE WASHINGTON COAST. THE 12Z RUN OF THE MODELS WERE
VERY SIMILAR SHOWING THE COLD FRONT ON THE CASCADES AROUND 18Z
AND WEAKENING AS IT MOVED THROUGH THE FORECAST AREA BY 06Z THIS
EVENING. AT 21Z PRECIPITATION HAD BEEN FALLING ALONG THE CASCADE
CREST FOR SEVERAL HOURS WHILE KELN JUST REPORTED RAIN...IN
ADDITION SURFACE PRESSURE WAS STILL FALLING ALONG THE EAST SLOPES
OF THE CASCADES. THIS PUTS THE TIMING OF THE FRONT 3-4 HOURS
SLOWER THAN PREVIOUS THINKING DUE MAINLY TO THE 150KT JET DIGGING
THE LOW AND SLOWING EASTWARD PROGRESSION. FOR LATE THIS AFTERNOON
AND EARLY EVENING PRECIPITATION WILL MOVE ACROSS THE FORECAST AREA
IN THE WARM SECTOR AHEAD OF THE COLD FRONT AND POPS WERE ADJUSTED
ACCORDINGLY. UP-GLIDE ALONG THE 285-295 ISENTROPIC SURFACE IS
IMPRESSIVE BUT THE STRETCHING FRONT HAS CUT-OFF THE MOISTURE TAP
FROM OUT IN THE PACIFIC. IN ADDITION LOCAL SOUNDING ARE INDICATING
A VERY DRY SUB- CLOUD LAYER AND ACROSS THE EASTERN ZONES SOUTHERLY
WINDS HAVE DRIED OUT THE LOWER ATMOSPHERE FURTHER. WHILE JUST
ABOUT ALL LOCATIONS WILL PICK UP MEASURABLE PRECIPITATION WITH THE
FRONT IT WILL TAKE A WHILE TO SATURATE THE LOWER ATMOSPHERE AND
PRECIPITATION WILL LOWERED. THE SOUTHERLY FLOW AHEAD OF THE FRONT
HAS KEPT SNOW LEVELS AT OR ABOVE 4000 FEET THROUGH EARLY EVENING.
FOR THE REST OF TONIGHT EXPECT DRYING FROM THE WEST BEHIND THE
FRONT. SOUTHWEST WINDS WILL INCREASE RESULTING IN THE TYPICAL RAIN
SHADOW ALONG THE EAST SLOPES OF THE CASCADES AND PROMOTING UP-
SLOPING FLOW ACROSS THE EASTERN ZONES. SNOW LEVELS ARE EXPECTED
TO DROP BEHIND THE FRONT TO NEAR THE SURFACE. BUT BY THAT TIME RAIN AND
SNOW WILL TURN SHOWERY AND THE BEST CHANCES FOR MEASURABLE
PRECIPITATION WILL ALONG THE CASCADE CREST AND THE PANHANDLE
MOUNTAINS. SOUTHWEST WINDS WILL INCREASE TO BREEZY WITH GUSTS
OVERNIGHT 20-25 MPH ACROSS A LARGE PORTION OF THE FORECAST AREA.
THIS SHOULD KEEP FOG AND STRATUS FORMATION TO A MINIMUM.
SATURDAY WEAK AND FAST MOVING HIGH PRESSURE WILL BUILD IN BEHIND
THE COLD FRONT. WESTERLY FLOW INTO THE EASTERN MOUNTAINS WILL
KEEP OROGRAPHIC SHOWERS IN THE FORECAST FOR THOSE ZONES.
BY SATURDAY AFTERNOON THE NEXT STORM SYSTEM WILL BE KNOCKING ON
THE DOOR. SOUTHWEST FLOW WILL INCREASE WARM AIR ADVECTION AND
MOISTURE INTO THE NORTH WEST ZONES. THE 12Z ANS NOW THE 18Z MODELS
ARE ALL PRETTY SIMILAR BRIDGING IN A WEAK SHORT WAVE DISTURBANCE
THROUGH THE NORTHWEST ZONES BETWEEN 18-00Z SATURDAY AFTERNOON. THE
COMBINATION OF THE ISENTROPIC LIFT AN THE WAVE WILL BE ENOUGH TO
SUPPORT LIKELY OR BETTER POPS ACROSS THE NORTHWEST ZONES BY LATE
IN THE AFTERNOON. SNOW LEVELS WILL BE DOWN TO THE VALLEY FLOOR AND
1 TO 2 INCHES OF NEW SNOW WILL BE POSSIBLE BY LATE SATURDAY
AFTERNOON. TEMPERATURES WILL BE 5-7 DEGREES COOLER SATURDAY AND
VERY NEAR SEASONAL NORMALS. /TOBIN
...MOIST PACIFIC STORM TO BRING CHANCE FOR MODERATE SNOWS ABOVE
2000 FEET SATURDAY NIGHT THROUGH MIDDAY SUNDAY...
SATURDAY NT THROUGH SUNDAY NT...THE NEXT IN A LINE OF
MOIST PACIFIC STORMS WILL IMPACT THE REGION BRINGING RAIN AND SNOW
AS WELL AS MODERATE WINDS. MODEL GUIDANCE IS GENERALLY FAIR TO
POOR WITH THIS SYSTEM AND THIS IS MAKING FOR QUITE THE FORECAST
CHALLENGE TRYING TO SORT OUT THE DETAILS. LOOKING AT THE BIG
PICTURE...A MOIST 1.4" PWAT PLUME...COLD CORE SHORTWAVE
ENERGY...AND STRONG UPPER-LEVEL JET DYNAMICS ALL COME TOGETHER
TOMORROW AFTERNOON OFF THE WASHINGTON COAST RESULTING IN STRONG
CYCLOGENESIS WHICH WILL TRANSITION ACROSS THE PAC NW SATURDAY NT
THROUGH MIDDAY SUNDAY. MODELS ARE HAVING AN EXTREMELY DIFFICULT
TIME WITH THE DETAILS REGARDING THE STRENGTH OF THE LOW- LEVEL
CYCLOGENESIS AS WELL AS THE TRACK. THE TREND OFF THE NAM/GEM/ECMWF
HAS BEEN TOWARD A SOUTHERN TRACK WHICH BRINGS THE SFC CYCLONE
ALONG THE WA/OR BORDER AND HEAVIEST PRECIPITATION ACROSS THE
SOUTHERN COLUMBIA BASIN WHILE THE LAST FEW RUNS OF THE GFS
CONTINUE WITH MUCH DEEPER LOW (NEARLY 10MB DEEPER THAN OTHER
GUIDANCE) AND TRACK DIRECTLY ACROSS THE CWA WHICH WOULD RESULT IN
HEAVY PRECIPITATION ACROSS THE CENTRAL AND NORTHERN TIER ZONES. WITH
THE EC/NAM/GEM IN MUCH BETTER AGREEMENT AND SHOWING SOME
CONSISTENCY WITHIN THE LAST TWO RUNS...WILL LEAN IN THAT DIRECTION
AND PUT LESS WEIGHT WITH THE OUTLYING GFS.
STRONG ISENTROPIC ASCENT ALONG THE 280-295K SURFACE DEVELOPING
SATURDAY NIGHT WILL JUST ABOUT GUARANTEE PRECIPITATION FOR ALL
LOCATIONS...STARTING IN THE CASCADES AND NORTHERN MTNS FIRST THEN
SPREADING ACROSS THE BASIN AFTER A SHALLOW DRY LAYER LEFT IN THE
WAKE OF SATURDAY`S SYSTEM BECOMES MOISTENED. BUT IT WILL BE THE
PRECIPITATION SHIELD THAT DEVELOPS ALONG THE NORTHERN PERIPHERY OF
THE LOW-LEVEL CYCLONE...OR TROWAL AIRSTREAM WHICH BECOMES THE
FOCUS FOR THE HEAVIEST AMOUNTS AS THE CYCLONE TRACKS ACROSS THE
REGION. AGAIN...THE FORECAST HAS TRENDED TOWARD THE NAM/EC/GEM AND
POPS/QPF WERE REDUCED ALONG THE NORTHERN TIER AND INCREASED FOR
NEAR THE WA/OR BORDER. THE SECOND MAJOR CHALLENGE WILL BE SNOW
LEVELS. WITH SUCH A WARM MOIST TAP OF MOISTURE (NEARLY 0.50"
TONGUE NOSING INTO THE BASIN)...EXPECT SNOW LEVELS TO RISE WITHIN
THE 2000-3500K FT RANGE ALONG THE SOUTHERN BASIN TO 1500-2000K FT
LAYER ACROSS THE NORTH. THIS MAY LEAD TO ANOTHER EVENT WHERE SNOW
FALLS ACROSS THE WEST PLAINS INCLUDING THE SPOKANE AIRPORT WITH A
FEW INCHES AND RAIN/SNOW MIX DOWNTOWN WITH LITTLE TO NO ACCUMULATIONS.
WITH CONFIDENCE GENERALLY POOR WITH THE STORM TRACK...AND WHERE
THE THE HEAVIEST PRECIPITATION BANDS WILL SET UP...WILL LEAVE OUT
EXACT SNOW AMTS IN THE AFD BUT POST PRELIMINARY SNOW AMTS ON
WEATHER STORY 2 LOCATED (WEATHER.GOV/SPOKANE). BY LATE SUNDAY
MORNING...THE SYSTEM BEGINS TO WEAKEN AND TRACKS INTO CENTRAL
IDAHO WITH STRONG WESTERLIES RAPIDLY INCREASING AS STRONG COLD
ADVECTION SLIDES DOWN THE CASCADES. THIS WILL QUICKLY SHUT OFF
THE PRECIPITATION FROM WEST TO EAST AT THE EXPENSE OF STRONG WINDS
DOWN THE EAST SLOPES...WATERVILLE PLATEAU...AND WESTERN BASIN.
WITH 850MB WINDS INCREASING TO 40-55KTS...EXPECT WINDS IN
LOCATIONS LIKE WENATCHEE TO GUSTS IN EXCESS OF 35-40KTS. /SB
MONDAY THROUGH FRIDAY...THE REGION WILL BE AFFECTED BY A WEAK
FRONTAL SYSTEM ON MONDAY...FOLLOWED BY A DRYING RIDGE MIDWEEK. A
STRONGER SYSTEM WILL AFFECT THE FORECAST AREA ON THANKSGIVING DAY.
WARM FRONTAL PRECIPITATION WILL SPREAD ACROSS THE INLAND NORTHWEST
ON MONDAY. THERE ARE SOME DIFFERENCES IN THE TRACK OF THE SHORTWAVE
TROUGH BUT GENERALLY THE BEST FORCING REMAINS TO OUR NORTH. THIS
WILL KEEP THE BEST CHANCE OF PRECIPITATION ACROSS OUR NORTHERN ZONES.
PRECIPITATION IS EXPECTED TO BE EITHER RAIN OR A MIX OF RAIN AND
SNOW SOUTH OF I-90 WITH MAINLY SNOW TO THE NORTH. THE NORTHERN
VALLEYS AND THE WATERVILLE PLATEAU COULD SEE LIGHT SNOWFALL
ACCUMULATIONS BUT ANY SIGNIFICANT SNOWFALL WILL BE CONFINED TO THE
ELEVATIONS ABOVE 3500 FEET. AS THE COLD FRONT PUSHES THROUGH MONDAY
NIGHT THE FOCUS FOR PRECIPITATION WILL SHIFT TO THE EASTERN
MOUNTAINS AND BECOME MORE SHOWERY IN NATURE. ON TUESDAY A MID LEVEL
RIDGE WILL START TO BUILD OVER THE REGION. THERE IS SOME MOISTURE IN
THE WESTERLY FLOW ALOFT ALONG WITH SOME ISENTROPIC ASCENT ACROSS THE
NORTHERN TIER BUT ANY PRECIPITATION THAT OCCURS WILL BE LIGHT.
DAYTIME TEMPERATURES WILL BE ON A GRADUAL WARMING TREND THROUGH
MIDWEEK. BY WEDNESDAY NIGHT...CLEARING SKIES AND LIGHT WINDS WILL
ALLOW FOG AND LOW STRATUS FORMATION IN THE BASIN. EXPECT THIS WILL
SPREAD NORTH TO THE NORTHEAST VALLEYS NOT AFFECTED BY CLOUDS
LINGERING ALONG THE BC BORDER.
...THANKSGIVING DAY LOOKS TO BE WET BUT NOT WHITE ACROSS THE INLAND
NORTHWEST...
A STRONGER PACIFIC WEATHER SYSTEM WILL AFFECT THE REGION BY
THANKSGIVING DAY. THIS SYSTEM HAS A NICE MOISTURE TAP WITH PWATS
AROUND 150 PERCENT OF NORMAL. WE COULD SEE A GOOD SHOT OF
PRECIPITATION BUT LOW LEVEL SOUTHERLY FLOW WILL HAVE PUSHED SNOW
LEVELS ABOVE MOST VALLEY FLOORS. BY THURSDAY NIGHT THE COLD FRONT
SWINGS THROUGH AND SNOW LEVELS WILL DROP OVERNIGHT. BY THIS TIME
MOST OF THE PRECIPITATION WILL HAVE MOVED EAST TO THE PANHANDLE
MOUNTAINS. TEMPERATURES WILL RETURN TO NEAR SEASONAL NORMALS. /KELCH
&&
.AVIATION...
A COLD FRONT WILL MOVE ACROSS THE FORECAST THIS AFTERNOON AND BE
EAST OF THE AREA BY THIS EVENING. PRECIPITATION AND LOWERING
CEILINGS WILL BE ON THE INCREASE TODAY. CONDITIONS WILL BE MAINLY
VFR WITH LOCALIZED AND BRIEF MVFR CEILINGS DURING THE HEAVIEST
PRECIPITATION. CONDITIONS WILL DRY OUT FROM THE WEST BEHIND THE COLD
FRONT AND EXPECT ENOUGH WIND TO KEEP THE LOWER ATMOSPHERE MIXED
ENOUGH FOR ONLY ISOLATED STRATUS DEVELOPMENT SATURDAY MORNING. /TOBIN
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 33 39 32 37 27 39 / 70 20 90 80 10 40
COEUR D`ALENE 33 39 31 37 28 40 / 80 20 80 70 20 50
PULLMAN 32 39 32 36 28 42 / 80 20 70 80 20 40
LEWISTON 36 47 36 41 30 48 / 70 10 40 90 20 30
COLVILLE 32 40 33 40 28 38 / 80 30 80 50 10 60
SANDPOINT 32 36 32 37 28 36 / 80 40 80 60 20 60
KELLOGG 32 33 30 34 27 35 / 90 70 90 90 40 60
MOSES LAKE 31 45 32 43 26 43 / 20 10 80 60 0 40
WENATCHEE 32 43 32 43 29 41 / 0 30 90 50 10 50
OMAK 28 43 31 42 25 40 / 20 60 90 60 0 60
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KPQR 202235
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
234 PM PST FRI NOV 20 2009
.SYNOPSIS...A STRONG COLD FRONT IS MOVING INTO THE CASCADES THIS
AFTERNOON WITH MUCH COLDER AIR ALOFT IN ITS WAKE...WITH SHOWERS AND
LOW SNOW LEVELS FOR THE REMAINDER OF TODAY AND TONIGHT. ANOTHER FRONT
ARRIVES LATER SAT...WITH STRONG WINDS POSSIBLE ON THE COAST AND
SIGNIFICANT SNOW EXPECTED IN THE CASCADES. THE NEXT STORM ARRIVES
LATER MON.
&&
.SHORT TERM...A COLD FRONT IS MOVING THROUGH THE CASCADES THIS
AFTERNOON. DOPPLER RADAR IS SHOWING SIGNIFICANT WITH THE FRONTAL
SYSTEM AND SHOWERS NOW MOVING ONSHORE AN INTO THE COASTAL RANGE AS
THE COLDER AIR ALOFT BRINGS A MORE UNSTABLE AIR MASS. UNSTABLE
AIRMASS GIVES THE POTENTIAL OF A FEW ISOLATED THUNDERSTORMS THIS
AFTERNOON...MAINLY OVER THE COAST AND COASTAL RANGE.
SNOW LEVELS ARE DROPPING BEHIND THE FRONT...MODELS BRING SNOW LEVELS
DOWN TO 3500 FEET THIS AFTERNOON. PRECIPITATION IS BECOMING MORE
SHOWERY IN NATURE...WITH 6 TO 10 INCHES OF NEW SNOW EXPECTED. WILL
CONTINUE CURRENT SNOW ADVISORY FOR CASCADES.
THE NEXT PACIFIC FRONTAL SYSTEM IS EXPECTED TO ARRIVE LATER
SATURDAY...WITH STRONG WINDS AND ANOTHER DECENT ROUND OF
PRECIPITATION. LATEST MODEL RUNS AGREEING ON BRINGING COASTAL WINDS
UP TO HIGH WIND CRITERIA WITH THIS NEXT SYSTEM AND WILL ISSUE HIGH
WIND WATCH FOR THE OREGON COAST FOR SATURDAY AFTERNOON AND EVENING.
WITH LOW SNOW LEVELS IN PLACE...VERY LIKELY WILL SEE SIGNIFICANT SNOW
IN THE CASCADES...AND POSSIBLY HIGHER RIDGES OF COAST RANGE. WITH
POTENTIAL FOR 12 TO 18 INCHES OF SNOW LATER SAT AND SAT NIGHT...WILL
ISSUE A WINTER STORM WATCH WITH AFTERNOON PACKAGE.
MODELS NOW INDICATE A BREAK IN THE ACTION FOR LATER SUNDAY AND SUN
NIGHT. EXPECT GENERALLY DRY CONDITIONS SUN EVENING. NEXT SYSTEM WILL
PUSH WARM FRONT TOWARDS THE COAST LATE SUN NIGHT. CURRENT MODELS SLOW
THE MONDAY SYSTEM AND TAKE THE BRUNT OF THE PRECIPITATION TO OUR
NORTH. WILL LEAVE A CHANCE OF PRECIPITATION IN ALL OF OUR AREA AND
CATEGORICAL POPS OVER THE NORTHERN ZONES. LIKENS
.LONG TERM...WEAK HIGH PRES BUILDS OVER THE FORECAST AREA MON NIGHT.
MODELS SHOW A WEAK SYSTEM APPROACH THE COAST EARLY TUE...BUT IT
TRACKS FURTHER NORTH AND LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF
THE CWA. THIS RIDGE IS MORE PERSISTENT THAN PREVIOUS MODEL RUNS
SUGGESTED. IT MANAGES TO DELAY THE ARRIVAL OF A SECOND SYSTEM
THROUGH THUR. BY MID NEXT WEEK...MODELS DISAGREE ON THE SOLUTION FOR
THE WEEKEND. GFS MODEL RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK
ON PRECIP THROUGH THURS NIGHT BUT THE CURRENT RUN SHOWS RAIN
EXTENDING TO THE CASCADES THURS NIGHT. SO FAR...MODELS SUGGEST A
FAIRLY NICE WEEKEND AS ANOTHER UPPER HIGH PRES TEMPORARILY SETS UP
OVER THE PAC NW. LRAMIREZ
&&
.AVIATION...FRONT A LITTLE SLOW MOVING EAST WHICH BROUGHT MORE MVFR
THAN EXPECTED...NOW THAT WE ARE POST FRONTAL EXPECT GENERALLY VFR
THIS EVENING EXCEPT IN MVFR SHOWERS. PROBABILITY OF MVFR CIGS AROUND
25 PERCENT.
KPDX AND APPROACHES...CONDITIONS ARE EXPECTED TO REMAIN PRIMARILY
VFR WITH SOME PATCHY MVFR CIGS IN SHOWERS. WOLFE
&&
.MARINE...SMALL CRAFT WINDS WILL CONTINUE THROUGH SATURDAY MORNING
BEFORE THE NEXT STRONGER FRONT BOOSTS GUSTS TO LOW END GALE CRITERIA
SATURDAY AFTERNOON WITH THE POSSIBILITY OF ANOTHER WAVE GENERATING
STRONG GALES AND POSSIBLY STORM FORCE WINDS BY LATE SATURDAY NIGHT.
SEAS CURRENTLY HOVERING AROUND 14 TO 15 FT AND SHOULD BUILD TO THE
UPPER TEENS WITH THE NEXT SYSTEMS. WOLFE
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
THROUGH SAT MORNING.
SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO
FLORENCE THROUGH SAT MORNING.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO
FLORENCE THROUGH SAT MORNING.
GALE WARNING CAPE SHOALWATER TO CASCADE HEAD SAT MORNING
THROUGH LATE SATURDAY NIGHT.
GALE WARNING CASCADE HEAD TO FLORENCE SAT MORNING THROUGH
SATURDAY EVENING.
STORM WATCH CASCADE HEAD TO FLORENCE SAT EVENING THROUGH
SUNDAY MORNING.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES FRI MORNING THROUGH SAT MORNING.
WINTER WEATHER WATCH FOR SNOW FOR THE SOUTH WASHINGTON AND
NORTH OREGON CASCADES AND THE CASCADES IN LANE COUNTY FOR
SATURDAY AFTERNOON THROUGH SUNDAY MORNING.
HIGH WIND WATCH FOR THE NORTHERN AND CENTRAL OREGON COAST
FOR SAT AFTERNOON AND NIGHT.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KOTX 202103
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
103 PM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION TODAY BRINGING VALLEY
RAIN AND MOUNTAIN SNOW. AFTER A SHORT BREAK IN THE WEATHER ON
SATURDAY...A STRONGER AND COLDER STORM SYSTEM WILL BRING THE
POTENTIAL FOR MOUNTAIN SNOW AND MODERATE VALLEY SNOW ACCUMULATIONS
SATURDAY NIGHT AND INTO SUNDAY. A SERIES OF STORM SYSTEMS WILL
CONTINUE TO PASS THROUGH THE INLAND NORTHWEST EVERY 24 TO 36 HOURS
WELL INTO NEXT WEEK.
&&
.DISCUSSION...
WENT AHEAD AND SLOWED THE TIMING OF THE PRECIPITATION BY 2-3 HOURS
FOR THIS AFTERNOON. THE FRONT IS HUNG UP ON THE CASCADES AND THE
BEST MOISTURE WIL;L BE ASSOCIATED WITH THE FRONT. IN ADDITION DRY
AIR MOVING IN FROM THE SOUTH AND IS CREATING A VERY DRY SUB-CLOUD
LAYER. WHILE RADAR IS PICKING UP ON SOME RETURNS THE PRECIPITATION
IS HAVING A HARD TIME SATURATING THE LOWER LAYERS. THINK THIS WILL
BE A MATTER OF TIME AND MOST LOCATIONS WILL SEE MEASURABLE
PRECIPITATION LATER THIS AFTERNOON. WITH THIS IN MIND BACKED OFF ON
PRECIPITATION AMOUNTS AS WELL. /TOBIN
&&
.AVIATION...
A COLD FRONT WILL MOVE ACROSS THE FORECAST THIS AFTERNOON AND BE
EAST OF THE AREA BY THIS EVENING. PRECIPITATION AND LOWERING
CEILINGS WILL BE ON THE INCREASE TODAY. CONDITIONS WILL BE MAINLY
VFR WITH LOCALIZED AND BRIEF MVFR CEILINGS DURING THE HEAVIEST
PRECIPITATION. CONDITIONS WILL DRY OUT FROM THE WEST BEHIND THE COLD
FRONT AND EXPECT ENOUGH WIND TO KEEP THE LOWER ATMOSPHERE MIXED
ENOUGH FOR ONLY ISOLATED STRATUS DEVELOPMENT SATURDAY MORNING. /TOBIN
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 47 33 39 32 40 29 / 50 70 20 90 80 10
COEUR D`ALENE 49 33 39 31 40 30 / 40 80 20 80 70 20
PULLMAN 50 32 39 32 39 30 / 20 80 20 70 80 20
LEWISTON 52 36 47 35 44 32 / 10 70 10 40 90 20
COLVILLE 46 32 40 32 41 30 / 70 80 30 80 50 10
SANDPOINT 47 32 36 31 37 30 / 40 80 40 80 60 20
KELLOGG 46 32 33 30 36 29 / 20 90 70 90 90 40
MOSES LAKE 50 31 45 31 45 27 / 60 20 10 80 60 0
WENATCHEE 46 32 43 30 45 29 / 60 0 30 90 50 10
OMAK 47 28 43 29 43 26 / 60 20 60 90 60 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KOTX 201801
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1001 AM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION TODAY BRINGING VALLEY
RAIN AND MOUNTAIN SNOW. AFTER A SHORT BREAK IN THE WEATHER ON
SATURDAY...A STRONGER AND COLDER STORM SYSTEM WILL BRING THE
POTENTIAL FOR MOUNTAIN SNOW AND MODERATE VALLEY SNOW ACCUMULATIONS
SATURDAY NIGHT AND INTO SUNDAY. A SERIES OF STORM SYSTEMS WILL
CONTINUE TO PASS THROUGH THE INLAND NORTHWEST EVERY 24 TO 36 HOURS
WELL INTO NEXT WEEK.
&&
.DISCUSSION...
ONLY MINOR GRID EDITS FOR TODAY AS FORECAST LOOKS TO BE ON TRACK.
THE COLD FRONT IS CURRENTLY MOVING EAST OF THE CASCADES AND THIS
SLOWS THE TIMING OF THE INCOMING PRECIPITATION BY A FEW HOURS
...BUT NOT ENOUGH TO CHANGE WORDING IN THE FORECAST. IT STILL
LOOKS LIKE MOST LOCATIONS WILL GET ANOTHER DOSE OF PRECIPITATION
JUST AHEAD OF THE COLD FRONT. /TOBIN
&&
.AVIATION...
A COLD FRONT WILL MOVE ACROSS THE FORECAST THIS AFTERNOON AND BE
EAST OF THE AREA BY THIS EVENING. PRECIPITATION AND LOWERING
CEILINGS WILL BE ON THE INCREASE TODAY. CONDITIONS WILL BE MAINLY
VFR WITH LOCALIZED AND BRIEF MVFR CEILINGS DURING THE HEAVIEST
PRECIPITATION. CONDITIONS WILL DRY OUT FROM THE WEST BEHIND THE COLD
FRONT AND EXPECT ENOUGH WIND TO KEEP THE LOWER ATMOSPHERE MIXED
ENOUGH FOR ONLY ISOLATED STRATUS DEVELOPMENT SATURDAY MORNING. /TOBIN
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 47 33 40 32 40 29 / 60 60 20 90 50 10
COEUR D`ALENE 49 33 39 31 40 30 / 50 70 20 90 70 20
PULLMAN 50 32 40 32 39 30 / 20 80 20 80 80 20
LEWISTON 52 36 47 35 44 32 / 10 60 10 70 70 10
COLVILLE 46 32 42 32 41 30 / 70 80 30 80 50 10
SANDPOINT 47 32 36 31 37 30 / 40 80 30 90 60 20
KELLOGG 46 32 32 30 36 29 / 20 90 70 90 80 60
MOSES LAKE 50 31 46 31 45 27 / 60 20 10 80 10 0
WENATCHEE 46 32 44 30 45 29 / 60 0 30 70 20 10
OMAK 47 28 44 29 43 26 / 60 20 50 90 20 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KSEW 201730
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST FRI NOV 20 2009
.SYNOPSIS...A FRONTAL SYSTEM OVER THE REGION WAS BREAKING UP AND
MOVING INLAND THIS MORNING. A TROUGH OF LOW PRESSURE OVER THE
COASTAL WATERS WILL MOVE INLAND AND FILL THIS AFTERNOON. A COOL
UPPER LEVEL TROUGH WILL MOVE OVER WASHINGTON TONIGHT. A FRONTAL
SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON SATURDAY AFTERNOON AND
NIGHT. A WEAKER FRONT WILL REACH THE AREA MONDAY. A RIDGE WILL BUILD
OVER THE REGION TUESDAY...WITH A FRONTAL SYSTEM POSSIBLE BY NEXT
THURSDAY.
&&
.SHORT TERM...FNTL SYS BREAKING UP WITH A PORTION INTO NRN
CALIF...AN AREA DISSIPATING OFF WA...AND ANOTHER UP OVER B.C. AND
THREE SFC LOW PRES CENTERS IN THE SFC LOW PRES TROF WHICH IS
STRETCHED OUT ALONG THE COAST FROM B.C. TO NRN CALIF. THE SFC TROF
MOVES INLAND THIS AFTERNOON AND FILLS. SHOWERS ON AND OFF THRU TNGT
UNDER A COOL UPPER TROF WHICH MOVES TO ERN WA LATER TONIGHT. A
FRONTAL SYSTEM WILL BE NEAR 130W BY DAYBREAK SATURDAY WITH THE WARM
FRONT SPREADING RAIN INTO WRN WA BY AFTERNOON AND A SFC LOW PRES
DEEPENING AND TRACKING TOWARD VANCOUVER ISLAND. THE SFC LOW DEEPENS
TO ARND A 990MB CENTER AND REACHES VRISL SAT EVENING AS THE COLD
FRONT MOVES THRU WRN WA. BY MIDDAY SUNDAY THE SFC LOW IS FILLING
OVER SOUTHERN B.C. AND THE WEATHER PATTERN OVER WRN WA IS THE
TYPICAL PSCZ PATTERN WITH PLENTY OF SNOW SHOWERS IN THE CASCADES.
THIS NEXT FNTL SYS SHUD MUSTER GALES FOR MOST OF THE MARINE AREAS
AND PERHAPS A WIND ADVISORY FOR WHIDBEY AND THE SAN JUANS SATURDAY
AFTERNOON BUT THIS SYSTEM WILL BE MUCH MORE TYPICAL THAN PREVIOUS
SYSTEMS. THE SYSTEM WILL BE WELL OCCLUDED AND COOLER THAN ALL THE
SYSTEMS THIS PAST WEEK SO THE SNOW LEVEL WILL STAY LOW. SHUD SEE
DECENT SNOWFALL IN THE CASCADES WITH THE FRONT SAT AFTERNOON AND
EVENING PLUS ADDITIONAL POSTFRONTAL OROGRAPHIC SNOW SHOWERS AND A
PSCZ SAT NITE THRU SUN MORNING. 19
.LONG TERM...WHILE THE OVERALL PATTERN CONTINUES TO LOOK FAIRLY
ACTIVE...THE EXPECTED SYSTEMS WILL BE WEAKER...WITH LESS WIND AND
RAIN AND BIGGER BREAKS IN BETWEEN. THE FRONTAL SYSTEM THAT HAS BEEN
ADVERTISED FOR MONDAY IS STILL ON TRACK AND IS EXPECTED TO SPREAD
RAIN ACROSS THE AREA DURING THE MORNING HOURS. THE AIR MASS WILL
START OUT RATHER COLD AHEAD OF THIS FRONT BUT WILL WARM UP AS IT
MOVES THROUGH. THIS IS THE BEGINNING OF HIGHER SNOW LEVELS FOR THE
FOLLOW UP SYSTEMS AS LOW AND MID LEVEL THICKNESSES INCREASE UNDER
HIGHER AVERAGE UPPER LEVEL HEIGHTS.
AT THIS TIME...I AM EXPECTING A RATHER DRY BENIGN DAY TUESDAY AS AN
UPPER LEVEL RIDGE PASSES OVERHEAD. THIS WILL BE FOLLOWED BY A WEAK
FRONT ON WEDNESDAY. BEYOND THAT DETAILS BECOME A BIT SKETCHY AS THE
MODELS ARE HAVING A BIT OF DIFFICULTY RESOLVING THE EVOLUTION OF THE
NEXT SYSTEM AS IT ROLLS ONSHORE LATER IN THE WEEK. CERNIGLIA
&&
.HYDROLOGY...IN THE OLYMPICS RAIN HAS ENDED EXCEPT FOR SCATTERED
SHOWERS. THE SNOW LEVEL IS ABOUT 3500 FEET AND WILL FALL FURTHER
TODAY. ALL THAT REMAINS IS FOR THE HEAVY RAIN FROM LAST NIGHT TO
DRAIN TO THE OCEAN. MOST RIVERS ARE FALLING BUT A FEW LONGER ONES
ARE STILL RISING TO THEIR CRESTS IN LOWER REACHES. THE DUNGENESS DID
NOT REACH FLOOD STAGE AND THE FLOOD WARNING FOR THAT RIVER WILL END
SOON. THE FLOOD WARNING FOR THE BOGACHIEL AND THE AREAL FLOOD
WARNING FOR CLALLAM AND JEFFERSON COUNTIES WILL REMAIN IN EFFECT
INTO THE AFTERNOON.
THE UPPER CHEHALIS IS RECEDING AND FLOOD WATCHES THERE HAVE ENDED.
THE LOWEST REACH OF THE CHEHALIS WILL BOUNCE AROUND AT A FOOT OR
LESS BELOW FLOOD STAGE THROUGH SATURDAY AND THE WATCH REMAINS IN
EFFECT THERE FOR TODAY AT LEAST. EVEN LOCAL INFLOW FROM THE WEAK
SYSTEM ON SATURDAY COULD CAUSE THE LOWER CHEHALIS TO APPROACH FLOOD
STAGE...BUT ANY FLOODING WILL BE MINOR.
THE CASCADES RECEIVED A BURST OF RAIN AS THE FRONT PASSED THIS
MORNING BUT RADAR SHOWS EVEN THAT IS DIMINISHING NOW. THE MT. BAKER
SKI AREA RECEIVED AROUND 3 INCHES OF WATER AFTER THE TEMPERATURES
ROSE ABOVE FREEZING YESTERDAY AND RAIN IS STILL FALLING AT A RATE OF
A TENTH OF AN INCH PER HOUR. THE NOOKSACK AND A FEW OTHER RIVERS
HAVE RISEN SHARPLY IN RESPONSE BUT NO FLOODING IS EXPECTED. RAINFALL
WAS CONSIDERABLY LESS IN THE CENTRAL CASCADES SO THE FLASHIER TOLT
AND PUYALLUP AT ORTING HAVE BARELY BUDGED...BUT WILL MONITOR THEM
TODAY.
ANOTHER SYSTEM WILL ARRIVE FROM THE WEST LATER SATURDAY WITH
SIGNIFICANT PRECIPITATION LATE SATURDAY INTO SATURDAY NIGHT.
HOWEVER...THIS SYSTEM IS COLDER WITH THE MAJORITY OF THE
PRECIPITATION BEING SNOW OVER THE MOUNTAINS. ACTUALLY MAY NEED NEED
WINTER WEATHER HEADLINES FOR THIS FEATURE AND NEW FLOODING IS NOT
EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH FAIRLY QUICKLY AND BE
WEAK ENOUGH TO NOT CAUSE ANY FLOODING...EVEN WITH RISING SNOW
LEVELS. FOR THE REMAINDER OF THE WEEK...THE AIR MASS OVER THE
NORTHWEST WILL BE WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE
SYSTEMS THAT ARE EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND
ARE NOT EXPECTED TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. BURKE
&&
.AVIATION...A FRONT WILL MOVE THROUGH WESTERN WASHINGTON THIS
MORNING. STRONG SW FLOW ALOFT WILL EASE OVERNIGHT AND BECOMING WLY.
THE ATMOSPHERE WILL BE MOIST AND SLIGHTLY UNSTABLE TODAY. THERE IS A
SLIGHT CHANCE OF ISOLATED THUNDERSTORMS THROUGH THIS AFTERNOON BUT
PROBABILITY IS TOO LOW TO INCLUDE IN TAFS.
EXPECT A PUGET SOUND CONVERGENCE ZONE TO FORM THIS EVENING FIRST
NEAR OR JUST NORTH OF KPAE...SAGGING SOUTH BETWEEN KPAE AND THE
KING/SNOHOMISH COUNTY BORDER BEFORE EVENTUALLY DISSIPATING LATER
TONIGHT.
ANOTHER STRONG FRONT WILL BRING STRONG SLY FLOW ALOFT ON SAT. RAIN
WILL INCREASE ACROSS THE AREA WITH AREAS OF MVFR CIGS/VIS EXPECTED.
KSEA...CIGS WILL GENERALLY REMAIN ABOVE 3K FT TODAY. THE FRONT WILL
MOVE PAST THE TERMINAL AROUND 17-18Z WITH LIGHT RAIN BECOMING
SHOWERY. A 15 PERCENT CHANCE OF A THUNDERSTORM NEAR THE
TERMINAL...WILL NOT INCLUDE IN TAF. GOOD MIXING AND WEAK INSTABILITY
OVERNIGHT WILL PROBABLY HINDER A LOWER STRATUS DECK OR FOG FROM
DEVELOPING TONIGHT. RAIN INCREASES ON SAT.
&&
.MARINE...STRONG SLY SURFACE FLOW WILL BECOME WESTERLY BEHIND A
SURFACE TROUGH THAT WILL SWEEP ACROSS THE AREA TODAY. THE STRONGEST
GALE FORCE WINDS WILL SHIFT FROM THE COAST TO THE CENTRAL/E STRAIT
THIS AFTERNOON AND TONIGHT. THE NEXT STRONG FRONT WILL LIKELY BRING
GALES TO THE COAST SAT...AND POSSIBLY THE N INTERIOR. WILL PROBABLY
PUT A GALE WATCH OR WARNING FOR THESE AREAS WITH THE AFTERNOON
FORECAST.
THE COLD FRONT IS EXPECTED TO MOVE ACROSS THE AREA SATURDAY
EVENING. ONSHORE FLOW WILL PREVAIL OVER THE WATERS ON SUNDAY BETWEEN
SYSTEMS. YET ANOTHER FRONTAL SYSTEM WILL AFFECT THE AREA ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES
LATE THIS AFTERNOON THROUGH TONIGHT.
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS TIL NOON
TODAY.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE COASTAL WATERS
FROM NOON THROUGH THIS EVENING.
.A GALE WARNING IS IN EFFECT FOR THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA THROUGH THIS EVENING.
.SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING WATERS
THROUGH THIS EVENING.
.A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KPQR 201638
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
838 AM PST FRI NOV 20 2009
.SYNOPSIS...A STRONG COLD FRONT MOVING ACROSS THE REGION THIS MORNING
WILL USHER IN MUCH COLDER AIR ALOFT...WITH SHOWERS AND LOW SNOW
LEVELS FOR REST OF TODAY AND TONIGHT. ANOTHER FRONT ARRIVES LATER
SAT...WITH SIGNIFICANT SNOW EXPECTED IN THE CASCADES. THE NEXT STORM
ARRIVES LATER MON.
&&
.SHORT TERM...A COLD FRONT IS MOVING THROUGH THE REGION THIS
MORNING...WITH THE CURRENT POSITION OF THE FRONT NEAR THE CASCADE
FOOTHILLS. LOW PRES DEVELOPMENT OFF CALIFORNIA COAST IS PULLING MOST
OF THE MOISTURE FROM OUR FRONT...SO OUR RAINFALL IS NOT AS HEAVY AS
EARLIER EXPECTED. THE HEAVIEST RAIN WILL BE TO OUR SOUTH...OVER SW
OREGON AND NW CALIFORNIA.
RAIN TURNS TO SHOWERS LATER THIS MORNING AND AFTERNOON AS THE COLDER
AIR ALOFT BRINGS A MORE UNSTABLE AIR MASS. WILL HAVE TO WATCH FOR
POTENTIAL OF A FEW ISOLATED THUNDERSTORMS THIS AFTERNOON. ALREADY
HAVE HAD A FEW STRIKES OFFSHORE...MAINLY SOUTH OF OUR AREA. WILL
CONTINUE ISOLATED TSTMS FOR THE COAST.
ONCE THE FRONT PASSES...SNOW LEVELS WILL DROP. STILL LOOKS REASONABLE
TO SEE SNOW LEVEL DOWN TO 3500 FEET BY MID AFTERNOON. PROBLEM IS THAT
PRECIPITATION WILL BECOME MORE SHOWERY IN NATURE. THIS WILL CREATE
WIDE RANGE OF SNOW ACCUMULATIONS...WITH 6 TO 10 INCHES EXPECTED. WILL
CONTINUE CURRENT SNOW ADVISORY FOR CASCADES.
SHOWERS DECREASING TONIGHT...BUT NEXT WAVE NOW PASSING 150W. THIS
SYSTEM ARRIVES LATER SATURDAY...WITH ANOTHER DECENT ROUND OF RAIN.
WITH LOW SNOW LEVELS IN PLACE...VERY LIKELY WILL SEE SIGNIFICANT SNOW
IN THE CASCADES...AND POSSIBLY HIGHER RIDGES OF COAST RANGE. NO
WARNINGS YET...BUT THIS BEARS WATCHING AS POTENTIAL FOR 12 TO 20
INCHES OF SNOW LATER SAT AND SAT NIGHT MAY PROMPT WINTER STORM WATCH
OR WARNING.
MODELS NOW INDICATE A BREAK IN THE ACTION FOR LATER SUNDAY AND SUN
NIGHT. EXPECT GENERALLY DRY CONDITIONS SUN EVENING. NEXT SYSTEM WILL
PUSH WARM FRONT TOWARDS THE COAST LATE SUN NIGHT...AT WHICH TIME WILL
BOOST POPS TO CHANCE. APPEARS BULK OF THE MON SYSTEM ARRIVES LATE
MON. LIKENS
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...LOW PRES
SYSTEM PUSHES INTO THE REGION BRINGING PLENTY OF RAIN AGAIN LATER
MON. HOWEVER...MODELS DISAGREE ON THE TIMING AND STRENGTH OF THIS
UPPER RIDGE. GFS SHOWS A WEAK RIDGE ENCOMPASSING THE AREA MON WITH A
CONTINUOUS FLOW OF RAIN. ECMWF SHOWS A STRONGER RIDGE MON NIGHT WITH
LITTLE RAIN. A HIGH WIND EVENT IS NOT EXPECTED OVER THE WEEKEND. A
WEAKER SECOND SYSTEM ARRIVES AROUND TUE...BUT IT TRACKS FURTHER TO
THE NORTH. BOTH THESE SYSTEMS ARE PROGRESSIVE SO DO NOT ANTICIPATE
PROLONGED PERIODS OF PRECIPITATION. MODELS INDICATE RIDGING BY
WED...YET KEPT POPS NEAR CLIMATOLOGY FOR THE EXTENDED PERIOD DUE TO
MODEL DIFFERENCES.
&&
.AVIATION...GENERALLY VFR TODAY EXCEPT IN MVFR SHOWERS. PROBABILITY
OF MVFR CIGS AROUND 25 PERCENT.
KPDX AND APPROACHES...CONDITIONS ARE EXPECTED TO REMAIN PRIMARILY
VFR WITH SOME POTENTIAL FOR MVFR CIGS THIS MORNING IN SHOWERS. WOLFE
&&
.MARINE...SMALL CRAFT WINDS WILL CONTINUE THROUGH SATURDAY MORNING
BEFORE THE NEXT STRONGER FRONT BOOSTS GUSTS TO LOW END GALE CRITERIA
SATURDAY AFTERNOON WITH THE POSSIBILITY OF ANOTHER WAVE GENERATING
STRONG GALES BY LATE SATURDAY NIGHT. SEAS CURRENTLY HOVERING IN THE
UPPER TEENS AND SLOWLY DECREASING TODAY TO AROUND 14 TO 15 FT. WOLFE
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
TODAY AND TONIGHT.
SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO
FLORENCE THROUGH SAT MORNING.
SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE
THROUGH SAT MORNING.
GALE WATCH CAPE SHOALWATER TO FLORENCE SAT THROUGH SUNDAY.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES FRI MORNING THROUGH SAT MORNING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KOTX 201141
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
342 AM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION TODAY BRINGING MOSTLY
VALLEY RAIN AND MOUNTAIN SNOW. AFTER A SHORT BREAK PERIOD ON
SATURDAY...A STRONGER AND COLDER STORM WILL BRING THE POTENTIAL
FOR MOUNTAIN SNOW AND MODERATE VALLEY SNOW ACCUMULATIONS SATURDAY
NIGHT AND INTO SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO
PASS THROUGH THE INLAND NORTHWEST EVERY 24 TO 36 HOURS WELL INTO NEXT
WEEK.
&&
.DISCUSSION...
TODAY THROUGH SATURDAY...SATELLITE CLEARLY INDICATES A MOIST
FRONTAL BAND IMPACTING THE PACIFIC COAST THIS MORNING. OUTRIDING
SHIELDS OF THICK MID AND HIGH LEVEL CLOUDS ARE CLOAKING THE
FORECAST AREA AHEAD OF THIS FRONT. THERE IS GOOD MODEL AGREEMENT
CONCERNING THE EVOLUTION OF THIS NEXT STORM SYSTEM. THE FRONTAL
BAND WILL SLOWLY MAKE IT`S WAY ACROSS THE FORECAST AREA TODAY AND
INTO TONIGHT. THE PARENT TROUGH IS BECOMING HIGHLY MERIDIONAL
WHICH WILL SERVE TO SLOW THE FRONT DOWN AS IT TRACKS
THROUGH...PROMOTING SUSTAINED SOUTHERLY MID LEVEL FLOW AHEAD OF
THE FRONT WHICH WILL KEEP SNOW LEVELS RELATIVELY HIGH TODAY. THIS
SOUTHERLY FLOW HAS BEEN RESPONSIBLE FOR ELEVATED OVERNIGHT
TEMPERATURES AT MANY LOCATIONS ACROSS THE EASTERN PART OF THE
FORECAST AREA. TODAY`S HIGH TEMPERATURES WILL PROBABLY OCCUR IN
THE MID MORNING AND THEN HOLD MORE OR LESS STEADY THROUGH THE
REST OF THE DAY. THE DEEPENING AND ELONGATING PARENT TROUGH WILL
ALSO SERVE TO STRETCH AND WEAKEN THE INCOMING PRECIPITABLE WATER
FEED. WHILE THE FRONTAL SURFACE IS STRONG IN THE MID LEVELS...AND
POSSES ES SOME GOOD JET AND DIFFERNTIAL VORTICITY SUPPORT...THE
OVERLAND FETCH ORIENTATION AND ASSOCIATED PRECIPITABLE WATER
VALUES ARE NOT CONDUCIVE TO HEAVY AMOUNTS OF RAIN AND MOUNTAIN
SNOW. THUS THERE IS REASONABLY HIGH CONFIDENCE OF LIGHT
PRECIPITATION...BEGINNING THIS MORNING OVER THE CASCADES AND DEEP
BASIN AND LATE THIS AFTERNOON OVER THE EASTERN THIRD OF THE
FORECAST AREA AND EARLY THIS EVENING IN THE IDAHO PANHANDLE.
AFTER A 3 TO 5 HOUR PERIOD OF LIGHT VALLEY RAIN AND MOUNTAIN
SNOW...THE FRONT WILL PASS THROUGH AND ALLOW BREEZY SOUTHWEST
WINDS TO DEVELOP OVERNIGHT ON THE TIGHTENING PRESSURE GRADIENT
BEHIND THE FRONT. COLD ADVECTION CROSSING THE CASCADES WILL ALLOW
A PRECIPITATION SHADOW TO DEVELOP OVER THE WESTERN BASIN...WHILE
THE SAME WESTERLY POST FRONT FLOW WILL PROMOTE THE USUAL LINGERING
OROGRAPHIC SHOWERS INTO THE IDAHO PANHANDLE THROUGH MOST OF THE
NIGHT. SNOW LEVELS WILL LOWER TO THE BASIN SURFACE OVERNIGHT...BUT
LINGERING PRECIPITATION OUTSIDE OF THE CASCADE CREST AREA AND
IDAHO PANHANDLE MOUNTAINS WILL BE SPOTTY AND MINOR.
ON SATURDAY THE FORECAST AREA WILL BE IN A BREAK PERIOD BETWEEN
SYSTEMS WITH A WEAK SHORT WAVE RIDGE BUILDING ALOFT. THE POST
FRONTAL AIR MASS WILL HAVE CAUSED AN AIR MASS EXCHANGE OF COOLER
AND DRIER AIR WHICH WILL LIMIT SATURDAY`S HIGHS TO ABOUT
NORMAL...AND PRIME THE AIR MASS FOR AN ONSET OF LIGHT SNOW EVEN IN
THE VALLEYS WITH THE NEXT INCOMING SYSTEM WHICH WILL BEGIN
IMPACTING THE CASCADES DURING THE AFTERNOON...BUT SHOULD HOLD OFF
UNTIL EVENING OVER THE EASTERN HALF OF THE FORECAST AREA. /FUGAZZI
SATURDAY NIGHT THROUGH THANKSGIVING DAY...
...MODERATE ACCUMULATING SNOWFALL FOR MOST VALLEY AND MOUNTAIN
LOCATIONS POSSIBLE SATURDAY NIGHT AND SUNDAY...
STILL GOOD RUN TO RUN CONSISTENCY AS FAR AS MODELS ADVERTISING A
SIGNIFICANT LOW PRESSURE SYSTEM THAT MAINTAINS A WELL ESTABLISHED
TAP INTO SUBTROPICAL MOISTURE AND OVERRUNS /OVERLAPS INTO THE
FAIRLY COLD CONDITIONALLY UNSTABLE AIR MASS LEFT IN THE WAKE OF
FRIDAY/FRIDAY NIGHTS WET FRONT PASSAGE. TENTATIVE SNOW
ACCUMULATION AMOUNTS WOULD BE ABOUT 1 TO 3 INCHES IN THE VALLEY
AND LOWLAND ELEVATIONS SATURDAY NIGHT INTO SUNDAY ABOVE 1500 FEET
MSL TO THE NORTH OF A WENATCHEE TO LEWISTON LINE...WITH SLIGHTLY
MORE THAN DOUBLE THAT...AROUND 4 TO 8 INCHES FOR THE MOUNTAINS
ABOVE 4000 FEET...WITH THESE GENERALIZED SNOW ACCUMULATION AMOUNTS IN
MIND THE MOST LIKELY PRODUCT UTILIZED TO HIGHLIGHT THIS EVENT
WILL MOST LIKELY BE WINTER WEATHER ADVISORIES FOR SNOW AT A LATER
TIME...FOR NOW WILL INSERT BLURB CONTAINING THESE GENERAL SNOW
ACCUMULATION AMOUNTS IN THE HAZARDOUS WEATHER OUTLOOK.
SUNDAY NIGHT SHORTWAVE RIDGING MOVES IN BEHIND THE EXITING
WEEKEND STORM SYSTEM RESULTING IN A DECREASE IN POPS UNTIL YET
ANOTHER QUICK MOVING FRONTAL SYSTEM WITH A SUBTROPICAL MOISTURE
TAP OVERRUNS COLD AIR IN PLACE AT LOW LEVELS TO INITIALLY START
OUT AS SNOWFALL AT MOST LOWER VALLEY ELEVATIONS SPREADING WEST TO
EAST MONDAY INTO MONDAY NIGHT THAT CHANGES OVER TO RAIN WITH TIME
FROM SOUTH TO NORTH AS LOW LEVEL WARM AIR ADVECTION BROUGHT ABOUT
BY THE PROLONGED SOUTHERLY FLOW BROUGHT ABOUT BY HOW THIS
PARTICULAR STORM APPROACHES AND MOVES THROUGH THE PACIFIC
NORTHWEST. ANOTHER BRIEF PERIOD OF SHORTWAVE RIDGING BETWEEN STORM
SYSTEMS MAY RESULT IN LOWER POPS FOR TUESDAY OVER MOST LOWLAND
LOCATIONS BUT IS MORE APPARENT TUESDAY NIGHT INTO
WEDNESDAY...ESPECIALLY NOTEWORTHY ARE IS THE EXPECTED RISE IN SNOW
LEVELS. MODELS CONTINUE TO ADVERTISE A WET THANKSGIVING DAY/THURSDAY
WITH YET ANOTHER FRONTAL ZONE/SUBTROPICAL MOISTURE TAP TYING INTO
A LOW PASSING THROUGH CENTRAL BRITISH COLUMBIA THAT GETS DRAGGED
WEST TO EAST THROUGH EASTERN WASHINGTON AND NORTHERN IDAHO.
/PELATTI
&&
.AVIATION...
A COLD FRONT AND ATTENDANT RAIN SHOWERS WILL MOVE EASTWARD ACROSS
THE AREA FRIDAY...MOVING INTO CENTRAL WASHINGTON AROUND MIDDAY AND
INTO EASTERN WA/N IDAHO BY LATE AFTERNOON/EARLY EVENING. MVFR CIGS
ARE EXPECTED AT KGEG/KSFF/KCOE/KPUW TOMORROW EVENING. AS THE LOW
LEVELS MOISTEN TOMORROW EVENING/NIGHT...LOW STRATUS DEVELOPMENT WILL
BE THE NEXT CONCERN...WITH IFR CIGS POSSIBLE. IN ADDITION...A
RAIN/SNOW MIX APPEARS POSSIBLE AT KPUW TOWARDS THE END OF THE
PRECIPITATION EVENT...WHICH COULD TEMPORARILY DROP VIS TO IFR.
/NEUMAN
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 47 33 40 32 40 29 / 60 60 20 90 50 10
COEUR D`ALENE 49 33 39 31 40 30 / 50 70 20 90 70 20
PULLMAN 50 32 40 32 39 30 / 20 80 20 80 80 20
LEWISTON 52 36 47 35 44 32 / 10 60 10 70 70 10
COLVILLE 46 32 42 32 41 30 / 70 80 30 80 50 10
SANDPOINT 47 32 36 31 37 30 / 40 80 30 90 60 20
KELLOGG 46 32 32 30 36 29 / 20 90 70 90 80 60
MOSES LAKE 50 31 46 31 45 27 / 60 20 10 80 10 0
WENATCHEE 46 32 44 30 45 29 / 60 0 30 70 20 10
OMAK 47 28 44 29 43 26 / 60 20 50 90 20 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KSEW 201141
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 AM PST FRI NOV 20 2009
.SYNOPSIS...A FRONTAL SYSTEM OVER THE AREA WILL GRADUALLY SHIFT EAST
TODAY ALLOWING COLDER AIR TO FILTER INTO WASHINGTON AND THE
PRECIPITATION TO GRADUALLY TAPER OFF. ANOTHER FRONTAL SYSTEM WILL
PASS ACROSS WESTERN WASHINGTON LATE SATURDAY FOR MORE RAIN AND
SOUTHERLY BREEZES. THIS WILL BE FOLLOWED BY YET ANOTHER...WEAKER
FRONT MONDAY. FOR TUESDAY INTO THURSDAY WE WILL HAVE LARGER BREAKS
BETWEEN PASSING FRONTS THAT WILL BE WEAKER WITH LESS PRECIPITATION.
&&
.SHORT TERM...A 982 MB SURFACE LOW IS JUST NORTH OF THE NORTHERN
TIP OF VANCOUVER ISLAND AND HEADED NORTH WHILE THE ASSOCIATED
BAROCLINIC BAND IS NEARLY STRAIGHT NORTH/SOUTH OVER THE COASTAL
WATERS AND BLEEDING EAST INTO WESTERN WASHINGTON AND OREGON. THIS
BAND WILL GRADUALLY SHIFT EAST THIS MORNING AS THE UPPER TROUGH
CLOSES IN AND GIVES IT A SHOVE. THUS EXPECT THE STEADIER
PRECIPITATION TO CONTINUE INTO LATER THIS MORNING BEFORE IT ALL
TAPERS TO SHOWERS. IT WILL STILL BE A BIT BREEZY TODAY BUT NOTHING
LIKE WHAT WE HAVE HAD THE LAST SEVERAL DAYS...JUST THE NORMAL TYPE
OF BLUSTERY. AS THE BAROCLINIC BAND MOVES ONSHORE COLDER AIR WILL
INVADE THE REGION BEHIND IT WITH SNOW LEVELS QUICKLY FALLING LATER
THIS AFTERNOON AND INTO THE EVENING HOURS.
AS FAR AS THE WINTER STORM WATCH FOR THE MOUNTAINS GOES...THE COLDER
AIR IS ONE INGREDIENT IN THE EQUATION FOR HEAVY SNOW...HOWEVER A
COUPLE OF THE OTHER INGREDIENTS WILL BE MISSING AS INDICATED ON
SATELLITE IMAGERY AND THE MODELS. THE UPPER TROUGH IS ELONGATING AS
IT MOVES ONSHORE WITH A SIGNIFICANT PORTION OF THE ENERGY COMING
ASHORE OVER NORTHERN CALIFORNIA/SOUTHERN OREGON. THAT IS WHERE THE
BULK OF THE FORCING AND ONSHORE FLOW WILL BE. THERE WILL ALSO BE A
LIMITED AMOUNT OF MOISTURE TO DEAL WITH. SO WITH THAT IN MIND
TRADED THE WINTER STORM WATCH FOR A WINTER WEATHER ADVISORY FOR THE
CASCADES WITH THE IDEA THAT FROM LATE THIS AFTERNOON THROUGH TONIGHT
THERE WILL GENERALLY BE A 6-10 INCH SNOWFALL WITH THE GREATER
AMOUNTS OVER THE VOLCANOES AND IN THE VICINITY OR JUST NORTH OF
STEVENS PASS DUE TO A WEAK CONVERGENCE ZONE ENHANCING THE SNOWFALL.
BY SATURDAY MORNING THERE WILL BE VERY LITTLE PRECIPITATION OVER THE
AREA BUT THAT IS ONLY BECAUSE IS IT THE QUIET BEFORE THE NEXT
APPROACHING SYSTEM. AS THIS FRONT APPROACHES...PRECIPITATION WILL
DEVELOP ACROSS WESTERN WASHINGTON DURING THE MIDDLE PART OF THE
DAY. ONCE THE PRECIPITATION BEGINS IT WILL LAST INTO SUNDAY MORNING
THEN TAPER OFF AS THE UPPER LEVEL SYSTEM PUSHES EAST OF THE CASCADES
DURING THE DAY. THIS WILL BE A WEAKER FRONT SO WHILE THERE WILL BE
A BIT OF A BREEZE...THERE ARE NOT EXPECTED TO BE ANY STRONG WINDS.
THIS WILL ALSO NOT POSE A PROBLEM FOR AREA RIVERS AS THE SNOW LEVEL
IS EXPECTED TO BE FAIRLY LOW FOR A PREDOMINATELY SNOW EVENT IN THE
MOUNTAINS.
BEING THAT WE WILL HAVE A COOL AIR MASS IN PLACE THROUGH THE
WEEKEND...TEMPERATURES WILL BE A BIT ON THE COOL SIDE. CERNIGLIA
.LONG TERM...WHILE THE OVERALL PATTERN CONTINUES TO LOOK FAIRLY
ACTIVE...THE EXPECTED SYSTEMS WILL BE WEAKER...WITH LESS WIND AND
RAIN AND BIGGER BREAKS IN BETWEEN. THE FRONTAL SYSTEM THAT HAS BEEN
ADVERTISED FOR MONDAY IS STILL ON TRACK AND IS EXPECTED TO SPREAD
RAIN ACROSS THE AREA DURING THE MORNING HOURS. THE AIR MASS WILL
START OUT RATHER COLD AHEAD OF THIS FRONT BUT WILL WARM UP AS IT
MOVES THROUGH. THIS IS THE BEGINNING OF HIGHER SNOW LEVELS FOR THE
FOLLOW UP SYSTEMS AS LOW AND MID LEVEL THICKNESSES INCREASE UNDER
HIGHER AVERAGE UPPER LEVEL HEIGHTS.
AT THIS TIME...I AM EXPECTING A RATHER DRY BENIGN DAY TUESDAY AS AN
UPPER LEVEL RIDGE PASSES OVERHEAD. THIS WILL BE FOLLOWED BY A WEAK
FRONT ON WEDNESDAY. BEYOND THAT DETAILS BECOME A BIT SKETCHY AS THE
MODELS ARE HAVING A BIT OF DIFFICULTY RESOLVING THE EVOLUTION OF THE
NEXT SYSTEM AS IT ROLLS ONSHORE LATER IN THE WEEK. CERNIGLIA
&&
.HYDROLOGY...RAIN CONTINUES TO FALL ACROSS THE AREA THIS MORNING
WITH HEAVY RAIN HAVING OCCURRED OVER THE OLYMPICS WITH 6 HR AMOUNTS
OF 1-3 INCHES COMMON. ACCORDING TO THE PRECIPITATION PROFILING
VERTICAL RADAR AT WESTPORT THE SNOW LEVEL HAS DROPPED FROM 6000 FEET
AROUND 10 PM LAST NIGHT TO 4000 FEET THIS MORNING. THIS DOWNWARD
TREND WILL CONTINUE AS THE MORNING PROGRESSES WHICH WILL HELP TO
BEGIN SHUTTING DOWN ADDITIONAL RUNOFF. AS A RESULT OF THIS HEAVY
RAIN A VARIETY OF FLOOD WARNINGS ARE IN EFFECT ACROSS THE OLYMPIC
PENINSULA.
WITH THE HEAVY PRECIPITATION HAVING BEEN FOCUSED OVER THE
OLYMPICS...THE CASCADES HAS BEEN SPARED THE HEAVY RAINS...ESPECIALLY
CONSIDERING THE BULK OF THE PRECIPITATION WAS IN THE FORM OF SNOW.
THUS THERE IS NO FLOODING CONCERNS FOR ANY OF THE RIVERS DRAINING
OFF THE CASCADES...INCLUDING THE GREEN RIVER.
ANOTHER SYSTEM IS FORECAST TO ARRIVE FROM THE WEST LATER SATURDAY
WITH SIGNIFICANT PRECIPITATION LATE SATURDAY INTO SATURDAY NIGHT.
HOWEVER...THIS SYSTEM IS COLDER WITH THE MAJORITY OF THE
PRECIPITATION BEING SNOW OVER THE MOUNTAINS. ACTUALLY MAY NEED NEED
WINTER WEATHER HEADLINES FOR THIS FEATURE AND ANY NEW FLOODING IS
NOT EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH FAIRLY QUICKLY AND BE
WEAK ENOUGH TO NOT CAUSE ANY FLOODING...EVEN WITH RISING SNOW
LEVELS. FOR THE REMAINDER OF THE WEEK...THE AIR MASS OVER THE
NORTHWEST WILL BE WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE
SYSTEMS THAT ARE EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND
ARE NOT EXPECTED TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
CERNIGLIA
&&
.AVIATION...AN UPPER TROF WILL MOVE ACROSS THE AREA...WITH A
WEAK...UPPER RIDGE MOVING OVER THE REGION LATE TONIGHT. STRONG SW
FLOW ALOFT RELAXING OVERNIGHT AND BECOMING WLY. EXPECT STRONG
ONSHORE OR WLY FLOW TO DEVELOP LATER TODAY BEHIND THE THE ASSOCIATED
SFC TROF. THE ONSHORE GRADIENT WILL THEN GRADUALLY RELAX OVERNIGHT.
EXPECT A PUGET SOUND CONVERGENCE ZONE /PSCZ/ TO DEVELOP THIS EVENING
/MOST LIKELY N OF KPAE/ BEHIND THE TROF PASSAGE. THE PSCZ MAY SAG
S BETWEEN KPAE AND THE KING/SNOHOMISH COUNTY BORDER BEFORE EVENTUALLY
DISSIPATING LATER TONIGHT.
CIGS WILL GENERALLY BE IN THE 3-6K FT RANGE TODAY...LIFTING INTO THE
4-7K FT RANGE OVERNIGHT. THERE MAY BE SOME CLEARING OVER THE SW
PORTION OF THE FORECAST AREA LATER TONIGHT...POSSIBLY RESULTING IN
AREAS OF CIGS NEAR 1500 FT...ALONG WITH PATCHY FOG REDUCING VSBYS
DOWN TO 3 SM.
KSEA...CIGS WILL GENERALLY BE IN THE 5-7K FT RANGE. THERE IS A
POSSIBILITY THAT THE CLOUDS MIGHT BECOME SCATTERED AT TIMES TONIGHT.
THE SANDPOINT PROFILER SHOWED WINDS ABOVE THE SFC...UP TO 2K FT...
CONTINUING TO WEAKEN. THUS WILL DROP THE MENTION OF LLWS.
&&
.MARINE...STRONG WESTERLY FLOW WILL DEVELOP BEHIND A SURFACE TROUGH
THAT WILL SWEEP ACROSS THE AREA TODAY. ANOTHER FRONTAL SYSTEM WILL
APPROACH THE AREA ON SATURDAY FOR INCREASED SOUTHERLY FLOW. THE COLD
FRONT IS EXPECTED TO MOVE ACROSS THE AREA SATURDAY EVENING. ONSHORE
FLOW WILL PREVAIL OVER THE WATERS ON SUNDAY BETWEEN SYSTEMS. ALAS...
YET ANOTHER FRONTAL SYSTEM WILL AFFECT THE AREA ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES
LATE THIS AFTERNOON THROUGH TONIGHT.
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS TIL NOON
TODAY.
.A GALE WARNING IS IN EFFECT FOR THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA THROUGH THIS EVENING.
.SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING
WATERS THROUGH THIS EVENING.
.A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 201038
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
238 AM PST FRI NOV 20 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION TODAY BRINGING MOSTLY
VALLEY RAIN AND MOUNTAIN SNOW. AFTER A SHORT BREAK PERIOD ON
SATURDAY...A STRONGER AND COLDER STORM WILL BRING THE POTENTIAL
FOR MOUNTAIN SNOW AND MODERATE VALLEY SNOW ACCUMULATIONS SATURDAY
NIGHT AND INTO SUNDAY. A SERIES OF STORM SYSTEMS WILL CONTINUE TO PASS
THROUGH THE INLAND NORTHWEST EVERY 24 TO 36 HOURS WELL INTO NEXT
WEEK.
&&
.DISCUSSION...
TODAY THROUGH SATURDAY...SATELLITE CLEARLY INDICATES A MOIST
FRONTAL BAND IMPACTING THE PACIFIC COAST THIS MORNING. OUTRIDING
SHIELDS OF THICK MID AND HIGH LEVEL CLOUDS ARE CLOAKING THE
FORECAST AREA AHEAD OF THIS FRONT. THERE IS GOOD MODEL AGREEMENT
CONCERNING THE EVOLUTION OF THIS NEXT STORM SYSTEM. THE FRONTAL
BAND WILL SLOWLY MAKE IT`S WAY ACROSS THE FORECAST AREA TODAY AND
INTO TONIGHT. THE PARENT TROUGH IS BECOMING HIGHLY MERIDIONAL
WHICH WILL SERVE TO SLOW THE FRONT DOWN AS IT TRACKS
THROUGH...PROMOTING SUSTAINED SOUTHERLY MID LEVEL FLOW AHEAD OF
THE FRONT WHICH WILL KEEP SNOW LEVELS RELATIVELY HIGH TODAY. THIS
SOUTHERLY FLOW HAS BEEN RESPONSIBLE FOR ELEVATED OVERNIGHT
TEMPERATURES AT MANY LOCATIONS ACROSS THE EASTERN PART OF THE
FORECAST AREA. TODAY`S HIGH TEMPERATURES WILL PROBABLY OCCUR IN
THE MID MORNING AND THEN HOLD MORE OR LESS STEADY THROUGH THE
REST OF THE DAY. THE DEEPENING AND ELONGATING PARENT TROUGH WILL
ALSO SERVE TO STRETCH AND WEAKEN THE INCOMING PRECIPITABLE WATER
FEED. WHILE THE FRONTAL SURFACE IS STRONG IN THE MID LEVELS...AND
POSSES ES SOME GOOD JET AND DIFFERNTIAL VORTICITY SUPPORT...THE
OVERLAND FETCH ORIENTATION AND ASSOCIATED PRECIPITABLE WATER
VALUES ARE NOT CONDUCIVE TO HEAVY AMOUNTS OF RAIN AND MOUNTAIN
SNOW. THUS THERE IS REASONABLY HIGH CONFIDENCE OF LIGHT
PRECIPITATION...BEGINNING THIS MORNING OVER THE CASCADES AND DEEP
BASIN AND LATE THIS AFTERNOON OVER THE EASTERN THIRD OF THE
FORECAST AREA AND EARLY THIS EVENING IN THE IDAHO PANHANDLE.
AFTER A 3 TO 5 HOUR PERIOD OF LIGHT VALLEY RAIN AND MOUNTAIN
SNOW...THE FRONT WILL PASS THROUGH AND ALLOW BREEZY SOUTHWEST
WINDS TO DEVELOP OVERNIGHT ON THE TIGHTENING PRESSURE GRADIENT
BEHIND THE FRONT. COLD ADVECTION CROSSING THE CASCADES WILL ALLOW
A PRECIPITATION SHADOW TO DEVELOP OVER THE WESTERN BASIN...WHILE
THE SAME WESTERLY POST FRONT FLOW WILL PROMOTE THE USUAL LINGERING
OROGRAPHIC SHOWERS INTO THE IDAHO PANHANDLE THROUGH MOST OF THE
NIGHT. SNOW LEVELS WILL LOWER TO THE BASIN SURFACE OVERNIGHT...BUT
LINGERING PRECIPITATION OUTSIDE OF THE CASCADE CREST AREA AND
IDAHO PANHANDLE MOUNTAINS WILL BE SPOTTY AND MINOR.
ON SATURDAY THE FORECAST AREA WILL BE IN A BREAK PERIOD BETWEEN
SYSTEMS WITH A WEAK SHORT WAVE RIDGE BUILDING ALOFT. THE POST
FRONTAL AIR MASS WILL HAVE CAUSED AN AIR MASS EXCHANGE OF COOLER
AND DRIER AIR WHICH WILL LIMIT SATURDAY`S HIGHS TO ABOUT
NORMAL...AND PRIME THE AIR MASS FOR AN ONSET OF LIGHT SNOW EVEN IN
THE VALLEYS WITH THE NEXT INCOMING SYSTEM WHICH WILL BEGIN
IMPACTING THE CASCADES DURING THE AFTERNOON...BUT SHOULD HOLD OFF
UNTIL EVENING OVER THE EASTERN HALF OF THE FORECAST AREA. /FUGAZZI
SATURDAY NIGHT THROUGH THANKSGIVING DAY...
...MODERATE ACCUMULATING SNOWFALL FOR MOST VALLEY AND MOUNTAIN
LOCATIONS POSSIBLE SATURDAY NIGHT AND SUNDAY...
STILL GOOD RUN TO RUN CONSISTENCY AS FAR AS MODELS ADVERTISING A
SIGNIFICANT LOW PRESSURE SYSTEM THAT MAINTAINS A WELL ESTABLISHED
TAP INTO SUBTROPICAL MOISTURE AND OVERRUNS /OVERLAPS INTO THE
FAIRLY COLD CONDITIONALLY UNSTABLE AIR MASS LEFT IN THE WAKE OF
FRIDAY/FRIDAY NIGHTS WET FRONT PASSAGE. TENTATIVE SNOW
ACCUMULATION AMOUNTS WOULD BE ABOUT 1 TO 3 INCHES IN THE VALLEY
AND LOWLAND ELEVATIONS SATURDAY NIGHT INTO SUNDAY ABOVE 1500 FEET
MSL TO THE NORTH OF A WENATCHEE TO LEWISTON LINE...WITH SLIGHTLY
MORE THAN DOUBLE THAT...AROUND 4 TO 8 INCHES FOR THE MOUNTAINS
ABOVE 4000 FEET...WITH THESE GENERALIZED SNOW ACCUMULATION AMOUNTS IN
MIND THE MOST LIKELY PRODUCT UTILIZED TO HIGHLIGHT THIS EVENT
WILL MOST LIKELY BE WINTER WEATHER ADVISORIES FOR SNOW AT A LATER
TIME...FOR NOW WILL INSERT BLURB CONTAINING THESE GENERAL SNOW
ACCUMULATION AMOUNTS IN THE HAZARDOUS WEATHER OUTLOOK.
SUNDAY NIGHT SHORTWAVE RIDGING MOVES IN BEHIND THE EXITING
WEEKEND STORM SYSTEM RESULTING IN A DECREASE IN POPS UNTIL YET
ANOTHER QUICK MOVING FRONTAL SYSTEM WITH A SUBTROPICAL MOISTURE
TAP OVERRUNS COLD AIR IN PLACE AT LOW LEVELS TO INITIALLY START
OUT AS SNOWFALL AT MOST LOWER VALLEY ELEVATIONS SPREADING WEST TO
EAST MONDAY INTO MONDAY NIGHT THAT CHANGES OVER TO RAIN WITH TIME
FROM SOUTH TO NORTH AS LOW LEVEL WARM AIR ADVECTION BROUGHT ABOUT
BY THE PROLONGED SOUTHERLY FLOW BROUGHT ABOUT BY HOW THIS
PARTICULAR STORM APPROACHES AND MOVES THROUGH THE PACIFIC
NORTHWEST. ANOTHER BRIEF PERIOD OF SHORTWAVE RIDGING BETWEEN STORM
SYSTEMS MAY RESULT IN LOWER POPS FOR TUESDAY OVER MOST LOWLAND
LOCATIONS BUT IS MORE APPARENT TUESDAY NIGHT INTO
WEDNESDAY...ESPECIALLY NOTEWORTHY ARE IS THE EXPECTED RISE IN SNOW
LEVELS. MODELS CONTINUE TO ADVERTISE A WET THANKSGIVING DAY/THURSDAY
WITH YET ANOTHER FRONTAL ZONE/SUBTROPICAL MOISTURE TAP TYING INTO
A LOW PASSING THROUGH CENTRAL BRITISH COLUMBIA THAT GETS DRAGGED
WEST TO EAST THROUGH EASTERN WASHINGTON AND NORTHERN IDAHO.
/PELATTI
&&
.AVIATION...
A COLD FRONT OFF THE COAST WILL MOVE EAST ON FRIDAY...MOVING INTO
CENTRAL WASHINGTON 15Z-21Z AND THEN INTO EASTERN WA/N IDAHO
21Z/20TH-06Z/21ST. MVFR CIGS ARE EXPECTED FOR
KGEG/KSFF/KCOE/KPUW/KLWS AS -RA DEVELOPS AND LOWER LEVELS OF THE
ATMOSPHERE MOISTEN. THEN IFR CONDITIONS ARE EXPECTED TO DEVELOP FOR
THESE SAME TAF SITES EXCEPT KLWS LATE IN THE TAF PERIOD AS ABUNDANT
LOW LEVEL MOISTURE AND UPSLOPE FLOW PRODUCE A LOW STRATUS DECK. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 47 33 40 32 40 29 / 60 60 20 90 50 10
COEUR D`ALENE 49 33 39 31 40 30 / 50 70 20 90 70 20
PULLMAN 50 32 40 32 39 30 / 20 80 20 80 80 20
LEWISTON 52 36 47 35 44 32 / 10 60 10 70 70 10
COLVILLE 46 32 42 32 41 30 / 70 80 30 80 50 10
SANDPOINT 47 32 36 31 37 30 / 40 80 30 90 60 20
KELLOGG 46 32 32 30 36 29 / 20 90 70 90 80 60
MOSES LAKE 50 31 46 31 45 27 / 60 20 10 80 10 0
WENATCHEE 46 32 44 30 45 29 / 60 0 30 70 20 10
OMAK 47 28 44 29 43 26 / 60 20 50 90 20 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KPQR 201029
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
228 AM PST FRI NOV 20 2009
.SYNOPSIS...A STRONG COLD FRONT MOVING ACROSS THE REGION THIS MORNING
WILL USHER IN MUCH COLDER AIR ALOFT...WITH SHOWERS AND LOW SNOW
LEVELS FOR REST OF TODAY AND TONIGHT. ANOTHER FRONT ARRIVES LATER
SAT...WITH SIGNIFICANT SNOW EXPECTED IN THE CASCADES. THE NEXT STORM
ARRIVES LATER MON.
&&
.SHORT TERM..COLD FRONT NOW PUSHING INLAND OVER THE REGION...WITH
CURRENT POSITION OF THE FRONT OVER THE COAST RANGE. LOW PRES
DEVELOPMENT OFF CALIFORNIA COAST IS ROBBING THE FRONT OF MOISTURE SO
RAINFALL NOT AS HEAVY AS EARLIER EXPECTED. HEAVIEST RAIN WILL BE TO
OUR SOUTH...OVER SW OREGON AND NW CALIFORNIA.
RAIN TURNS TO SHOWERS LATER THIS MORNING AND AFTERNOON AS THE COLDER
AIR ALOFT USHERS IN MORE UNSTABLE AIR MASS. WILL HAVE TO WATCH FOR
POTENTIAL OF A FEW ISOLATED THUNDERSTORMS THIS AFTERNOON. ALREADY
HAVE HAD A FEW STRIKES OFFSHORE. SUSPECT THIS MAY BE CASE THROUGH
JUST ABOUT ANY TIME TODAY. WILL INCLUDE ISOLATED TSTORMS FOR COAST.
ONCE THE FRONT PASSES...SNOW LEVELS WILL QUICKLY TUMBLE. STILL LOOKS
REASONABLE TO SEE SNOW LEVEL DOWN TO 3500 FEET BY MID AFTERNOON.
PROBLEM IS THAT PRECIPITATION WILL BECOME MORE SHOWERY IN NATURE.
THIS WILL CREATE WIDE RANGE OF SNOW ACCUMULATIONS...WITH 6 TO 10
INCHES EXPECTED. WILL CONTINUE CURRENT SNOW ADVISORY FOR CASCADES.
SHOWERS DECREASING TONIGHT...BUT NEXT WAVE NOW PASSING 150W. THIS
SYSTEM ARRIVES LATER SATURDAY...WITH ANOTHER DECENT ROUND OF RAIN.
WITH LOW SNOW LEVELS IN PLACE...VERY LIKELY WILL SEE SIGNIFICANT SNOW
IN THE CASCADES...AND POSSIBLY HIGHER RIDGES OF COAST RANGE. NO
WARNINGS YET...BUT THIS BEARS WATCHING AS POTENTIAL FOR 12 TO 20
INCHES OF SNOW LATER SAT AND SAT NIGHT MAY PROMPT WINTER STORM WATCH
OR WARNING. AGAIN...NOTHING YET AS WILL LET LATER SHIFTS EXAMINE.
MODELS NOW INDICATE A BREAK IN THE ACTION FOR LATER SUNDAY AND SUN
NIGHT. WILL TREND TO DECREASING SHOWERS ON SUN...WITH GENERALLY DRY
CONDITIONS SUN EVENING. NEXT SYSTEM WILL PUSH WARM FRONT TOWARDS THE
COAST LATE SUN NIGHT...AT WHICH TIME WILL BOOST POPS TO CHANCE.
APPEARS BULK OF THE MON SYSTEM ARRIVES LATE MON. ROCKEY.
.LONG TERM...NO CHANGES. LOW PRES SYSTEM PUSHES INTO THE REGION
BRINGING PLENTY OF RAIN AGAIN LATER MON. HOWEVER...MODELS DISAGREE ON
THE TIMING AND STRENGTH OF THIS UPPER RIDGE. GFS SHOWS A WEAK RIDGE
ENCOMPASSING THE AREA MON WITH A CONTINUOUS FLOW OF RAIN. ECMWF SHOWS
A STRONGER RIDGE MON NIGHT WITH LITTLE RAIN. A HIGH WIND EVENT IS NOT
EXPECTED OVER THE WEEKEND. A WEAKER SECOND SYSTEM ARRIVES AROUND
TUE...BUT IT TRACKS FURTHER TO THE NORTH. BOTH THESE SYSTEMS ARE
PROGRESSIVE SO DO NOT ANTICIPATE PROLONGED PERIODS OF PRECIPITATION.
MODELS INDICATE RIDGING BY WED...YET KEPT POPS NEAR CLIMATOLOGY FOR
THE EXTENDED PERIOD DUE TO MODEL DIFFERENCES.
&&
.AVIATION...STRONG COASTAL WINDS WILL DIMINISH GRADUALLY THROUGH THE
EARLY MORNING HOURS WITH BREEZY CONDITIONS INLAND. MVFR CONDITIONS
WILL IMPROVE TO A MIX OF MVFR AND VFR CONDITIONS ALONG THE COAST AS
THE FRONTAL SYSTEM MOVES INLAND THIS MORNING. CONDITIONS ARE
EXPECTED TO REMAIN PREDOMINANTLY VFR IN THE INTERIOR.
KPDX AND APPROACHES...RAIN WILL INCREASE AS THE FRONTAL SYSTEM MOVES
INLAND TODAY HOWEVER CEILING AND VISIBILITY CONDITIONS ARE EXPECTED
TO PRIMARILY REMAIN VFR. BREEZY SOUTHWESTERLY WINDS WILL INCREASE
THIS AFTERNOON AND EVENING.
&&
.MARINE...WINDS HAVE DIMINISHED TO GALES AS A FRONTAL WAVE
DEVELOPING OFF OF THE NORTHERN CALIFORNIA COAST HAS WEAKENED THE
COLD FRONT STRETCHED OVER COASTAL WATERS. GALE GUSTS WILL CONTINUE
THROUGH MIDDAY AS WINDS SHIFT TO THE SW AND THEN WNW AS THE FRONT
AND SUPPORTING UPPER LEVEL TROUGH SWING ONSHORE. SEAS CURRENTLY 20
TO 25 FT WILL SUBSIDE INTO THE UPPER TEENS BY THIS AFTERNOON. BRISK
NORTHWEST WINDS TONIGHT WILL EASE BY SATURDAY MORNING...BUT ANOTHER
SIGNIFICANT GALE IS POSSIBLE WITH THE NEXT FRONTAL SYSTEM LATER
SATURDAY AND SATURDAY NIGHT.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING ALL WATERS THROUGH NOON.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
TODAY AND TONIGHT.
HIGH SURF ADVISORY FOR SOUTH WASHINGTON AND NORTH
AND CENTRAL OREGON COAST THROUGH EARLY FRI MORNING..
FLOOD WATCH FOR SOUTHWEST WA AND EXTREME NW OREGON
THROUGH FRI NIGHT.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES FRI MORNING THROUGH SAT MORNING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KSEW 200607 AAB
AFDSEW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
1007 PM PST THU NOV 19 2009
UPDATED THE MARINE SEGMENT.
.SYNOPSIS...WIND AND RAIN WILL CONTINUE THIS EVENING BUT WILL
GRADUALLY DIMINISH FROM THE WEST OVERNIGHT AS A FRONT MOVES ACROSS
THE AREA. FRIDAY WILL BE COOL AND SHOWERY AS A DEEP UPPER LEVEL
TROUGH MOVES INLAND. ANOTHER FRONTAL SYSTEM WILL MOVE THROUGH THE
AREA ON SATURDAY. YET ANOTHER FRONT WILL MOVE ACROSS THE AREA ON
MONDAY. THE FRONTS THIS WEEKEND AND EARLY NEXT WEEK WILL NOT BE AS
VIGOROUS AS THE ONES THAT HAVE PASSED THROUGH THE AREA OVER THE PAST
WEEK.
&&
.SHORT TERM...AT 830 PM A STRONG FRONTAL SYSTEM SITS FROM JUST WEST
OF CAPE FLATTERY ON THE NORTH COAST SSW INTO THE OREGON OFFSHORE
WATERS. VERY STRONG SOUTH WINDS CONTINUE ALONG THE WASHINGTON COAST
THIS EVENING WITH MARINE STORM CONDITIONS AND LAND-BASED HIGH WIND
WARNING CONDITIONS ON THE IMMEDIATE COASTLINE. HIGH WINDS ARE
PEAKING AT THIS TIME AND SHOULD RELAX BY MIDNIGHT FROM NORTH TO
SOUTH. IN THE NORTH INTERIOR WIND HAS BEEN SLOW TO COME UP DUE TO A
RATHER STRONG EASTERLY COMPONENT TO THE FLOW. WITH SATELLITE IMAGERY
SHOWS THE CENTER OF A 980-985 MB SURFACE LOW JUST OFF THE CENTRAL
COAST OF VANCOUVER ISLAND MATURING AND MOVING NORTH...EXPECT
GRADIENTS TO BECOME MORE SELY AS THE LOW MOVES NORTH OF 50N. WHILE
WIND MAY FALL SHORT OF HIGH WIND CRITERIA BY 5 MPH IN THE NORTH
INTERIOR...40 MPH WITH GUSTS TO 58 MPH...THEY MAY BRIEFLY COME UP
WITH THE FRONTAL PASSAGE. SO WILL LET THE WARNING CONTINUE IN THAT
AREA UNTIL MIDNIGHT AS CURRENTLY IN PLACE.
RAINFALL HAS BEEN HEAVY IN THE NORTH PORTION OF THE OLYMPIC
PENINSULA. SEE THE HYDROLOGY SECTION BELOW CONCERNING NEW FLOODING
IN THAT AREA THAT IS OCCURRING AS A RESULT. RAIN SHOULD TAPER OFF TO
SHOWERS FROM THE WEST OVER THE NEXT 2-4 HOURS.
SNOW LEVELS IN THE MOUNTAINS HAVE RISEN TODAY WITH ALL MOUNTAIN
SITES NOW REPORTING RAIN OR MIXED PRECIPITATION. SNOW LEVELS WILL
FALL TO AROUND 4000 FT EARLY FRI AND DOWN TO AROUND 2000 FEET FRI
NIGHT AS A DEEP UPPER TROUGH MOVES THROUGH THE AREA. INCOMING 00Z
MODELS SHOW LESS PRECIPITATION AND LESS OROGRAPHIC WESTERLY FLOW
THAN PREVIOUS SOLUTIONS. WILL LOOK AT THE INCOMING HIGH
RESOLUTION MM5 DATA BEFORE MAKING THE DECISION TO DROP THE WINTER
STORM WATCH FOR THE MOUNTAINS FRI AFTERNOON THRU FRI NIGHT.
ANOTHER SYSTEM WILL MOVE ACROSS THE REGION LATER SAT. THIS FRONT
APPEARS TO BE PROGRESSIVE AND COOLER. WIND CONDITIONS SHOULD BE MORE
OF A TYPICAL MARINE CONCERN WITH MORE COMMON MODERATE TO STRONG
FRONTS AND PRECIPITATION AMOUNTS SHOULD BE MORE MODEST THAN THE PAST
SEVERAL FRONTAL FEATURES. NO UPDATES PLANNED AT THIS TIME. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...MODELS SHOW A
WARM FRONT CLIPPING WESTERN WASHINGTON...POSSIBLY ON MONDAY. HOWEVER
THE ECMWF SHOWS THE BULK OF THE MOISTURE AIMED AT SOUTHERN B.C. A
SHORT WAVE TROUGH WILL THEN TRAVERSE THE REGION MON NIGHT OR TUE
MORNING. FORECAST CONFIDENCE MID WEEK AND BEYOND REMAINS LOW AT THIS
POINT AS MODELS ARE OUT OF PHASE. THE UPPER LEVEL RIDGE MAY
RE-AMPLIFY OVER THE PAC NW...BUT THERE IS ANOTHER SYSTEM DEVELOPING
IN THE GULF OF AK WITH THE BAROCLINIC BAND SLIDING SE ACROSS
SOUTHERN B.C. AND PERHAPS INTO WESTERN WA. 33
&&
.HYDROLOGY...HEAVY RAIN HAS FALLEN THIS EVENING OVER THE NORTHERN
PORTION OF THE OLYMPIC PENINSULA. AS A RESULT FLOOD WARNINGS WERE
ISSUED FOR THE DUNGENESS RIVER AND AREA FLOOD WARNINGS WERE ISSUED
FOR THE OTHER RIVERS IN CLALLAM AND JEFFERSON COUNTIES. THE
SKOKOMISH AND SATSOP RIVERS STAY ABOVE FLOOD STAGE.
THE HEAVY BAND OF PRECIPITATION OVER THE NORTH OLYMPICS WILL
GRADUALLY MOVE EAST...AND PRECIPITATION RATES WITHIN THE BAND WILL
TAPER OFF AS THE COLD FRONT NOW MOVING ONSHORE PUSHES INLAND
OVERNIGHT.
THE UPPER CHEHALIS AND ITS TRIBUTARIES ARE FORECAST TO STAY BELOW
FLOOD STAGE...BUT THE LOWER CHEHALIS COULD STILL FLOOD. A WATCH
REMAINS IN EFFECT FOR THE WHOLE CHEHALIS SYSTEM.
RAINFALL AMOUNTS IN THE CASCADES DO NOT APPEAR TO BE ENOUGH TO CAUSE
FLOODING. RIVERS WILL RISE BUT WILL NOT REACH FLOOD STAGE.
ANOTHER SYSTEM IS FORECAST TO ARRIVE FROM THE NORTHWEST ON SATURDAY
NIGHT...BUT THIS SYSTEM IS COLDER AND LESS LIKELY TO PRODUCE HEAVY
RAIN. 500 MB HEIGHTS DIP INTO THE 520S AS THE UPPER LEVEL TROUGH
MOVES INLAND SO MOST OF THIS PRECIPITATION WILL BE MOUNTAIN SNOW.
ANOTHER SYSTEM ON MONDAY SHOULD BE PROGRESSIVE ENOUGH TO NOT CAUSE
ANY FLOODING. A SYSTEM NEXT THURSDAY COULD BE WETTER AND WARMER BUT
MODELS DIFFER IN SIGNIFICANT DETAILS. THE FOLLOWING WEEKEND COULD
SEE SPLIT FLOW WITH MOST OF THE NEXT SYSTEM HEADING SOUTH OF
WASHINGTON.
AT NO TIME IS ANY FLOODING FORECAST ON THE GREEN RIVER.
BURKE/ALBRECHT
&&
.AVIATION...FROM THE PREVIOUS DISCUSSION...A COLD FRONT LIES
OFFSHORE...EXTENDING SW FROM NEAR THE N WA COAST. A STRONG SURFACE
LOW MOVING NE UP THE COLD FRONT WILL CURVE N...CROSSING N VANCOUVER
ISLAND 06Z. THE COLD FRONT WILL MOVE INLAND LATE TONIGHT. EXPECT
ANOTHER ROUND OF LOW LEVEL WIND SHEAR DUE TO 925 MB /2500 FT/ WINDS
INCREASING BACK TO 40-55 KT. SAND POINT PROFILER SHOWS S WINDS 50 KT
AT 2K FT. EXPECT CIGS TO DECREASE BACK DOWN TO MVFR LATE TONIGHT
AFTER THE WINDS WEAKEN.
KSEA...MAIN PROBLEM REMAINS LOW LEVEL WINDS AFFECTING APPROACHES.
CIGS LOWERING OVERNIGHT. KAM
&&
.MARINE...A COLD FRONT...EXTENDING FROM A 983 MB LOW ABOUT 70 NM SW
OF VANCOUVER ISLAND...WILL MOVE ACROSS THE AREA LATE TONIGHT AND
EARLY FRI MORNING. THE SURFACE LOW WILL CONTINUE MOVING NE. EXPECT A
SURFACE TROUGH TO SWEEP ACROSS THE AREA FRI AFTERNOON...RESULTING IN
STRONG WESTERLY FLOW BEHIND IT. ANOTHER COLD FRONT WILL MOVE ACROSS
THE WATERS LATE SATURDAY. ALAS...ANOTHER FRONTAL SYSTEM WILL AFFECT
THE AREA ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
A HIGH WIND WARNING REMAINS IN EFFECT FOR THE COAST AND NORTH
INTERIOR TIL MIDNIGHT TONIGHT.
A WIND ADVISORY IS IN EFFECT FOR SEATTLE TACOMA EVERETT
BREMERTON AREAS...EAST PUGET SOUND LOWLANDS...HOOD CANAL UNTIL
MIDNIGHT TONIGHT.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR THE COAST TIL 4 AM
FRI.
A WINTER STORM WATCH IS IN EFFECT FOR THE CASCADES FROM FRI
AFTERNOON THROUGH LATE FRI NIGHT.
PZ...STORM WARNINGS REMAIN IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
GALE WARNINGS ARE IN EFFECT FOR THE REMAINING WATERS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 200559
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
959 PM PST THU NOV 19 2009
.SYNOPSIS...
A COLD FRONT WILL BRING ANOTHER ROUND OF PRECIPITATION TO THE
INLAND NORTHWEST ON FRIDAY AND FRIDAY NIGHT. PRECIPITATION WILL
MAINLY BE RAIN FOR THE LOW ELEVATIONS...AND LIGHT AMOUNTS OF SNOW
ARE EXPECTED IN THE MOUNTAINS. THE UNSETTLED WEATHER PATTERN WILL
CONTINUE THROUGH THE WEEKEND. A VIGOROUS WEATHER SYSTEM WILL BRING
THE POTENTIAL FOR LOW ELEVATION SNOW SATURDAY NIGHT INTO SUNDAY
MORNING...MAINLY NORTH OF INTERSTATE 90.
&&
.DISCUSSION...
SOME FORECAST UPDATES HAVE BEEN SENT OUT FOR THE REST OF TONIGHT.
SATELLITE SHOWS A DEEP MOISTURE FEED FOCUSED ALONG A COLD FRONT
BOUNDARY WHICH EXTENDS FROM 130W OFF THE NORTHERN CALIFORNIA COAST
NORTHEAST INTO NORTHWEST WASHINGTON INCLUDING THE NORTH WASHINGTON
CASCADES. WITH THE MAIN SFC LOW OF 985MB NEAR VANCOUVER ISLAND
MOVING NORTH AND A WAVE DEVELOPING ALONG THE SOUTH SIDE OF THE
COLD FRONT...THE RESULT IS A COLD FRONT WHICH IS BECOMING MORE
NORTH-SOUTH ORIENTED. THIS WILL SLOW THE EASTWARD PROGRESSION OF
THE FRONT TONIGHT...RESULTING IN DRY CONDITIONS FOR MOST OF THE
AREA. THE ONE EXCEPTION IS THE CASCADES WHERE SOME PRECIPITATION
WILL CONTINUE. RADAR COMPOSITES SHOWS THE BULK OF THE PRECIPITATION
OVER NW WASHINGTON SO ONLY LIGHT ADDITIONAL ACCUMULATIONS EXPECTED
THE REST OF TONIGHT FOR THE CASCADES. SNOW LEVELS HAVE ALSO RISEN
TO 3000 TO 4000 FEET. THUS THE WINTER STORM WARNING IS NO LONGER
IN EFFECT.
FOR TEMPERATURES AND WINDS TONIGHT...A SE GRADIENT EXIST ACROSS
THE AREA WITH MESO SCALE FEATURES ALTERING THE GRADIENTS/WINDS.
WITH DOWNSLOPE FLOW OFF THE BLUE MTNS INTO WALLA WALLA...A LEESIDE
SFC TROUGH OF 1008MB HAS DEVELOPED WHICH IS ENHANCING THE PRESSURE
GRADIENT OVER SE WASHINGTON. THIS WILL RESULT IN SOUTHEAST WINDS
OF 5 TO 15 MPH THROUGH THE NIGHT FOR AREAS LIKE
SPOKANE...PULLMAN...LEWISTON...AND RITZVILLE. WITH WINDS PERSISTING AND
850MB TEMPS WARMING THROUGH THE NIGHT PER 00Z NAM SOLUTION LOW
TEMPERATURES FOR MOST LOCATIONS HAVE OCCURRED ALREADY OR ARE
OCCURRING NOW. MOSTLY CLOUDY SKIES WILL ALSO AID IN KEEPING
TEMPERATURE UP. A 1015MB MESO HIGH OVER N IDAHO WILL KEEP LIGHTER
NE WINDS PERSISTING NORTH AND EAST OF SPOKANE KEEPING LOW TEMPS A
LITTLE BIT COOLER IN THE LOWER TO MID 30S. COOLER TEMPS IN THE 30S
WILL ALSO BE COMMON IN THE CASCADES AND WENATCHEE AREA WITH MOST
AREAS RECEIVING LIGHTER WINDS. JW
&&
.AVIATION...
A COLD FRONT OFF THE COAST WILL MOVE EAST ON FRIDAY...MOVING INTO
CENTRAL WASHINGTON 15Z-21Z AND THEN INTO EASTERN WA/N IDAHO
21Z/20TH-06Z/21ST. MVFR CIGS ARE EXPECTED FOR
KGEG/KSFF/KCOE/KPUW/KLWS AS -RA DEVELOPS AND LOWER LEVELS OF THE
ATMOSPHERE MOISTEN. THEN IFR CONDITIONS ARE EXPECTED TO DEVELOP FOR
THESE SAME TAF SITES EXCEPT KLWS LATE IN THE TAF PERIOD AS ABUNDANT
LOW LEVEL MOISTURE AND UPSLOPE FLOW PRODUCE A LOW STRATUS DECK. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 40 46 31 39 32 40 / 0 30 60 30 90 50
COEUR D`ALENE 33 46 32 39 31 40 / 0 20 70 40 90 70
PULLMAN 39 48 31 38 32 39 / 0 20 80 30 80 80
LEWISTON 41 51 34 45 35 44 / 0 0 60 20 70 70
COLVILLE 32 46 32 41 32 41 / 10 50 80 30 80 50
SANDPOINT 32 45 31 36 31 37 / 10 20 80 50 90 60
KELLOGG 34 44 31 34 30 36 / 0 10 90 70 90 80
MOSES LAKE 41 49 30 43 31 45 / 10 50 10 10 80 10
WENATCHEE 36 47 31 42 30 45 / 10 30 10 20 70 20
OMAK 40 45 27 40 29 43 / 20 60 20 20 90 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KSEW 200519 AAA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PST THU NOV 19 2009
.SYNOPSIS...WIND AND RAIN WILL CONTINUE THIS EVENING BUT WILL
GRADUALLY DIMINISH FROM THE WEST OVERNIGHT AS A FRONT MOVES ACROSS
THE AREA. FRIDAY WILL BE COOL AND SHOWERY AS A DEEP UPPER LEVEL
TROUGH MOVES INLAND. ANOTHER FRONTAL SYSTEM WILL MOVE THROUGH THE
AREA ON SATURDAY. YET ANOTHER FRONT WILL MOVE ACROSS THE AREA ON
MONDAY. THE FRONTS THIS WEEKEND AND EARLY NEXT WEEK WILL NOT BE AS
VIGOROUS AS THE ONES THAT HAVE PASSED THROUGH THE AREA OVER THE PAST
WEEK.
&&
.SHORT TERM...AT 830 PM A STRONG FRONTAL SYSTEM SITS FROM JUST WEST
OF CAPE FLATTERY ON THE NORTH COAST SSW INTO THE OREGON OFFSHORE
WATERS. VERY STRONG SOUTH WINDS CONTINUE ALONG THE WASHINGTON COAST
THIS EVENING WITH MARINE STORM CONDITIONS AND LAND-BASED HIGH WIND
WARNING CONDITIONS ON THE IMMEDIATE COASTLINE. HIGH WINDS ARE
PEAKING AT THIS TIME AND SHOULD RELAX BY MIDNIGHT FROM NORTH TO
SOUTH. IN THE NORTH INTERIOR WIND HAS BEEN SLOW TO COME UP DUE TO A
RATHER STRONG EASTERLY COMPONENT TO THE FLOW. WITH SATELLITE IMAGERY
SHOWS THE CENTER OF A 980-985 MB SURFACE LOW JUST OFF THE CENTRAL
COAST OF VANCOUVER ISLAND MATURING AND MOVING NORTH...EXPECT
GRADIENTS TO BECOME MORE SELY AS THE LOW MOVES NORTH OF 50N. WHILE
WIND MAY FALL SHORT OF HIGH WIND CRITERIA BY 5 MPH IN THE NORTH
INTERIOR...40 MPH WITH GUSTS TO 58 MPH...THEY MAY BRIEFLY COME UP
WITH THE FRONTAL PASSAGE. SO WILL LET THE WARNING CONTINUE IN THAT
AREA UNTIL MIDNIGHT AS CURRENTLY IN PLACE.
RAINFALL HAS BEEN HEAVY IN THE NORTH PORTION OF THE OLYMPIC
PENINSULA. SEE THE HYDROLOGY SECTION BELOW CONCERNING NEW FLOODING
IN THAT AREA THAT IS OCCURRING AS A RESULT. RAIN SHOULD TAPER OFF TO
SHOWERS FROM THE WEST OVER THE NEXT 2-4 HOURS.
SNOW LEVELS IN THE MOUNTAINS HAVE RISEN TODAY WITH ALL MOUNTAIN
SITES NOW REPORTING RAIN OR MIXED PRECIPITATION. SNOW LEVELS WILL
FALL TO AROUND 4000 FT EARLY FRI AND DOWN TO AROUND 2000 FEET FRI
NIGHT AS A DEEP UPPER TROUGH MOVES THROUGH THE AREA. INCOMING 00Z
MODELS SHOW LESS PRECIPITATION AND LESS OROGRAPHIC WESTERLY FLOW
THAN PREVIOUS SOLUTIONS. WILL LOOK AT THE INCOMING HIGH
RESOLUTION MM5 DATA BEFORE MAKING THE DECISION TO DROP THE WINTER
STORM WATCH FOR THE MOUNTAINS FRI AFTERNOON THRU FRI NIGHT.
ANOTHER SYSTEM WILL MOVE ACROSS THE REGION LATER SAT. THIS FRONT
APPEARS TO BE PROGRESSIVE AND COOLER. WIND CONDITIONS SHOULD BE MORE
OF A TYPICAL MARINE CONCERN WITH MORE COMMON MODERATE TO STRONG
FRONTS AND PRECIPITATION AMOUNTS SHOULD BE MORE MODEST THAN THE PAST
SEVERAL FRONTAL FEATURES. NO UPDATES PLANNED AT THIS TIME. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...MODELS SHOW A
WARM FRONT CLIPPING WESTERN WASHINGTON...POSSIBLY ON MONDAY. HOWEVER
THE ECMWF SHOWS THE BULK OF THE MOISTURE AIMED AT SOUTHERN B.C. A
SHORT WAVE TROUGH WILL THEN TRAVERSE THE REGION MON NIGHT OR TUE
MORNING. FORECAST CONFIDENCE MID WEEK AND BEYOND REMAINS LOW AT THIS
POINT AS MODELS ARE OUT OF PHASE. THE UPPER LEVEL RIDGE MAY
RE-AMPLIFY OVER THE PAC NW...BUT THERE IS ANOTHER SYSTEM DEVELOPING
IN THE GULF OF AK WITH THE BAROCLINIC BAND SLIDING SE ACROSS
SOUTHERN B.C. AND PERHAPS INTO WESTERN WA. 33
&&
.HYDROLOGY...HEAVY RAIN HAS FALLEN THIS EVENING OVER THE NORTHERN
PORTION OF THE OLYMPIC PENINSULA. AS A RESULT FLOOD WARNINGS WERE
ISSUED FOR THE DUNGENESS RIVER AND AREA FLOOD WARNINGS WERE ISSUED
FOR THE OTHER RIVERS IN CLALLAM AND JEFFERSON COUNTIES. THE
SKOKOMISH AND SATSOP RIVERS STAY ABOVE FLOOD STAGE.
THE HEAVY BAND OF PRECIPITATION OVER THE NORTH OLYMPICS WILL
GRADUALLY MOVE EAST...AND PRECIPITATION RATES WITHIN THE BAND WILL
TAPER OFF AS THE COLD FRONT NOW MOVING ONSHORE PUSHES INLAND
OVERNIGHT.
THE UPPER CHEHALIS AND ITS TRIBUTARIES ARE FORECAST TO STAY BELOW
FLOOD STAGE...BUT THE LOWER CHEHALIS COULD STILL FLOOD. A WATCH
REMAINS IN EFFECT FOR THE WHOLE CHEHALIS SYSTEM.
RAINFALL AMOUNTS IN THE CASCADES DO NOT APPEAR TO BE ENOUGH TO CAUSE
FLOODING. RIVERS WILL RISE BUT WILL NOT REACH FLOOD STAGE.
ANOTHER SYSTEM IS FORECAST TO ARRIVE FROM THE NORTHWEST ON SATURDAY
NIGHT...BUT THIS SYSTEM IS COLDER AND LESS LIKELY TO PRODUCE HEAVY
RAIN. 500 MB HEIGHTS DIP INTO THE 520S AS THE UPPER LEVEL TROUGH
MOVES INLAND SO MOST OF THIS PRECIPITATION WILL BE MOUNTAIN SNOW.
ANOTHER SYSTEM ON MONDAY SHOULD BE PROGRESSIVE ENOUGH TO NOT CAUSE
ANY FLOODING. A SYSTEM NEXT THURSDAY COULD BE WETTER AND WARMER BUT
MODELS DIFFER IN SIGNIFICANT DETAILS. THE FOLLOWING WEEKEND COULD
SEE SPLIT FLOW WITH MOST OF THE NEXT SYSTEM HEADING SOUTH OF
WASHINGTON.
AT NO TIME IS ANY FLOODING FORECAST ON THE GREEN RIVER.
BURKE/ALBRECHT
&&
.AVIATION...FROM THE PREVIOUS DISCUSSION...A COLD FRONT LIES
OFFSHORE...EXTENDING SW FROM NEAR THE N WA COAST. A STRONG SURFACE
LOW MOVING NE UP THE COLD FRONT WILL CURVE N...CROSSING N VANCOUVER
ISLAND 06Z. THE COLD FRONT WILL MOVE INLAND LATE TONIGHT. EXPECT
ANOTHER ROUND OF LOW LEVEL WIND SHEAR DUE TO 925 MB /2500 FT/ WINDS
INCREASING BACK TO 40-55 KT. SAND POINT PROFILER SHOWS S WINDS 50 KT
AT 2K FT. EXPECT CIGS TO DECREASE BACK DOWN TO MVFR LATE TONIGHT
AFTER THE WINDS WEAKEN.
KSEA...MAIN PROBLEM REMAINS LOW LEVEL WINDS AFFECTING APPROACHES.
CIGS LOWERING OVERNIGHT. KAM
&&
.MARINE...A COLD FRONT EXTENDING SOUTHWEST FROM THE NORTH WASHINGTON
COAST WILL MOVE INLAND OVER NIGHT...AS A STRONG 985 MB LOW ABOUT 250
NM W OF CAPE FLATTERY MOVES NE ACROSS NORTHERN VANCOUVER ISLAND THIS
EVENING. COASTAL STORM FORCE AND INLAND GALE FORCE WINDS WILL EASE
BEHIND THE SYSTEM LATE TONIGHT. WESTERLY GALES WILL DEVELOP COAST
AND STRAIT ON FRIDAY AS THE MAIN LOW PRESSURE TROUGH FURTHER
OFFSHORE FINALLY MOVES INLAND. ANOTHER COLD FRONT WILL REACH AFFECT
THE AREA SATURDAY...WITH POST-FRONT ONSHORE FLOW SUNDAY. YET ANOTHER
FRONTAL SYSTEM WILL ARRIVE ON MONDAY.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
A HIGH WIND WARNING REMAINS IN EFFECT FOR THE COAST AND NORTH
INTERIOR TIL MIDNIGHT TONIGHT.
A WIND ADVISORY IS IN EFFECT FOR SEATTLE TACOMA EVERETT
BREMERTON AREAS...EAST PUGET SOUND LOWLANDS...HOOD CANAL UNTIL
MIDNIGHT TONIGHT.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR THE COAST TIL 4 AM
FRI.
A WINTER STORM WATCH IS IN EFFECT FOR THE CASCADES FROM FRI
AFTERNOON THROUGH LATE FRI NIGHT.
PZ...STORM WARNINGS REMAIN IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
GALE WARNINGS ARE IN EFFECT FOR THE REMAINING WATERS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 200517
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PST THU NOV 19 2009
.SYNOPSIS...WIND AND RAIN WILL CONTINUE THIS EVENING BUT WILL
GRADUALLY DIMINISH FROM THE WEST OVERNIGHT AS A FRONT MOVES ACROSS
THE AREA. FRIDAY WILL BE COOL AND SHOWERY AS A DEEP UPPER LEVEL
TROUGH MOVES INLAND. ANOTHER FRONTAL SYSTEM WILL MOVE THROUGH THE
AREA ON SATURDAY. YET ANOTHER FRONT WILL MOVE ACROSS THE AREA ON
MONDAY. THE FRONTS THIS WEEKEND AND EARLY NEXT WEEK WILL NOT BE AS
VIGOROUS AS THE ONES THAT HAVE PASSED THROUGH THE AREA OVER THE PAST
WEEK.
&&
.SHORT TERM...AT 830 PM A STRONG FRONTAL SYSTEM SITS FROM JUST WEST
OF CAPE FLATTERY ON THE NORTH COAST SSW INTO THE OREGON OFFSHORE
WATERS. VERY STRONG SOUTH WINDS CONTINUE ALONG THE WASHINGTON COAST
THIS EVENING WITH MARINE STORM CONDITIONS AND LAND-BASED HIGH WIND
WARNING CONDITIONS ON THE IMMEDIATE COASTLINE. HIGH WINDS ARE
PEAKING AT THIS TIME AND SHOULD RELAX BY MIDNIGHT FROM NORTH TO
SOUTH. IN THE NORTH INTERIOR WIND HAS BEEN SLOW TO COME UP DUE TO A
RATHER STRONG EASTERLY COMPONENT TO THE FLOW. WITH SATELLITE IMAGERY
SHOWS THE CENTER OF A 980-985 MB SURFACE LOW JUST OFF THE CENTRAL
COAST OF VANCOUVER ISLAND MATURING AND MOVING NORTH...EXPECT
GRADIENTS TO BECOME MORE SELY AS THE LOW MOVES NORTH OF 50N. WHILE
WIND MAY FALL SHORT OF HIGH WIND CRITERIA BY 5 MPH IN THE NORTH
INTERIOR...40 MPH WITH GUSTS TO 58 MPH...THEY MAY BRIEFLY COME UP
WITH THE FRONTAL PASSAGE. SO WILL LET THE WARNING CONTINUE IN THAT
AREA UNTIL MIDNIGHT AS CURRENTLY IN PLACE.
RAINFALL HAS BEEN HEAVY IN THE NORTH PORTION OF THE OLYMPIC
PENINSULA. SEE THE HYDROLOGY SECTION BELOW CONCERNING NEW FLOODING
IN THAT AREA THAT IS OCCURRING AS A RESULT. RAIN SHOULD TAPER OFF TO
SHOWERS FROM THE WEST OVER THE NEXT 2-4 HOURS.
SNOW LEVELS IN THE MOUNTAINS HAVE RISEN TODAY WITH ALL MOUNTAIN
SITES NOW REPORTING RAIN OR MIXED PRECIPITATION. SNOW LEVELS WILL
FALL TO AROUND 4000 FT EARLY FRI AND DOWN TO AROUND 2000 FEET FRI
NIGHT AS A DEEP UPPER TROUGH MOVES THROUGH THE AREA. INCOMING 00Z
MODELS SHOW LESS PRECIPITATION AND LESS OROGRAPHIC WESTERLY FLOW
THAN PREVIOUS SOLUTIONS. WILL LOOK AT THE INCOMING HIGH
RESOLUTION MM5 DATA BEFORE MAKING THE DECISION TO DROP THE WINTER
STORM WATCH FOR THE MOUNTAINS FRI AFTERNOON THRU FRI NIGHT.
ANOTHER SYSTEM WILL MOVE ACROSS THE REGION LATER SAT. THIS FRONT
APPEARS TO BE PROGRESSIVE AND COOLER. WIND CONDITIONS SHOULD BE MORE
OF A TYPICAL MARINE CONCERN WITH MORE COMMON MODERATE TO STRONG
FRONTS AND PRECIPITATION AMOUNTS SHOULD BE MORE MODEST THAN THE PAST
SEVERAL FRONTAL FEATURES. NO UPDATES PLANNED AT THIS TIME. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...MODELS SHOW A
WARM FRONT CLIPPING WESTERN WASHINGTON...POSSIBLY ON MONDAY. HOWEVER
THE ECMWF SHOWS THE BULK OF THE MOISTURE AIMED AT SOUTHERN B.C. A
SHORT WAVE TROUGH WILL THEN TRAVERSE THE REGION MON NIGHT OR TUE
MORNING. FORECAST CONFIDENCE MID WEEK AND BEYOND REMAINS LOW AT THIS
POINT AS MODELS ARE OUT OF PHASE. THE UPPER LEVEL RIDGE MAY
RE-AMPLIFY OVER THE PAC NW...BUT THERE IS ANOTHER SYSTEM DEVELOPING
IN THE GULF OF AK WITH THE BAROCLINIC BAND SLIDING SE ACROSS
SOUTHERN B.C. AND PERHAPS INTO WESTERN WA. 33
&&
.HYDROLOGY...HEAVY RAIN HAS FALLEN THIS EVENING OVER THE NORTHERN
PORTION OF THE OLYMPIC PENINSULA. AS A RESULT FLOOD WARNINGS WERE
ISSUED FOR THE DUNGENESS RIVER AND AREA FLOOD WARNINGS WERE ISSUED
FOR THE OTHER RIVERS IN CLALLAM AND JEFFERSON COUNTIES. THE
SKOKOMISH AND SATSOP RIVERS STAY ABOVE FLOOD STAGE.
THE HEAVY BAND OF PRECIPITATION OVER THE NORTH OLYMPICS WILL
GRADUALLY MOVE EAST...AND PRECIPITATION RATES WITHIN THE BAND WILL
TAPER OFF AS THE COLD FRONT NOW MOVING ONSHORE PUSHES INLAND
OVERNIGHT.
THE UPPER CHEHALIS AND ITS TRIBUTARIES ARE FORECAST TO STAY BELOW
FLOOD STAGE...BUT THE LOWER CHEHALIS COULD STILL FLOOD. A WATCH
REMAINS IN EFFECT FOR THE WHOLE CHEHALIS SYSTEM.
RAINFALL AMOUNTS IN THE CASCADES DO NOT APPEAR TO BE ENOUGH TO CAUSE
FLOODING. RIVERS WILL RISE BUT WILL NOT REACH FLOOD STAGE.
ANOTHER SYSTEM IS FORECAST TO ARRIVE FROM THE NORTHWEST ON SATURDAY
NIGHT...BUT THIS SYSTEM IS COLDER AND LESS LIKELY TO PRODUCE HEAVY
RAIN. 500 MB HEIGHTS DIP INTO THE 520S AS THE UPPER LEVEL TROUGH
MOVES INLAND SO MOST OF THIS PRECIPITATION WILL BE MOUNTAIN SNOW.
ANOTHER SYSTEM ON MONDAY SHOULD BE PROGRESSIVE ENOUGH TO NOT CAUSE
ANY FLOODING. A SYSTEM NEXT THURSDAY COULD BE WETTER AND WARMER BUT
MODELS DIFFER IN SIGNIFICANT DETAILS. THE FOLLOWING WEEKEND COULD
SEE SPLIT FLOW WITH MOST OF THE NEXT SYSTEM HEADING SOUTH OF
WASHINGTON.
AT NO TIME IS ANY FLOODING FORECAST ON THE GREEN RIVER.
BURKE/ALBRECHT
&&
.AVIATION...DELAYED. WILL BE ADDED BY 10 PM.
&&
.MARINE...DELAYED. WILL BE ADDED BY 10 PM.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
A HIGH WIND WARNING REMAINS IN EFFECT FOR THE COAST AND NORTH
INTERIOR TIL MIDNIGHT TONIGHT.
A WIND ADVISORY IS IN EFFECT FOR SEATTLE TACOMA EVERETT
BREMERTON AREAS...EAST PUGET SOUND LOWLANDS...HOOD CANAL UNTIL
MIDNIGHT TONIGHT.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR THE COAST TIL 4 AM
FRI.
A WINTER STORM WATCH IS IN EFFECT FOR THE CASCADES FROM FRI
AFTERNOON THROUGH LATE FRI NIGHT.
PZ...STORM WARNINGS REMAIN IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
GALE WARNINGS ARE IN EFFECT FOR THE REMAINING WATERS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KOTX 200459
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
859 PM PST THU NOV 19 2009
.SYNOPSIS...
A COLD FRONT WILL BRING ANOTHER ROUND OF PRECIPITATION TO THE
INLAND NORTHWEST ON FRIDAY AND FRIDAY NIGHT. PRECIPITATION WILL
MAINLY BE RAIN FOR THE LOW ELEVATIONS...AND LIGHT AMOUNTS OF SNOW
ARE EXPECTED IN THE MOUNTAINS. THE UNSETTLED WEATHER PATTERN WILL
CONTINUE THROUGH THE WEEKEND. A VIGOROUS WEATHER SYSTEM WILL BRING
THE POTENTIAL FOR LOW ELEVATION SNOW SATURDAY NIGHT INTO SUNDAY
MORNING...MAINLY NORTH OF INTERSTATE 90.
&&
.DISCUSSION...
SOME FORECAST UPDATES HAVE BEEN SENT OUT FOR THE REST OF TONIGHT.
SATELLITE SHOWS A DEEP MOISTURE FEED FOCUSED ALONG A COLD FRONT
BOUNDARY WHICH EXTENDS FROM 130W OFF THE NORTHERN CALIFORNIA COAST
NORTHEAST INTO NORTHWEST WASHINGTON INCLUDING THE NORTH WASHINGTON
CASCADES. WITH THE MAIN SFC LOW OF 985MB NEAR VANCOUVER ISLAND
MOVING NORTH AND A WAVE DEVELOPING ALONG THE SOUTH SIDE OF THE
COLD FRONT...THE RESULT IS A COLD FRONT WHICH IS BECOMING MORE
NORTH-SOUTH ORIENTED. THIS WILL SLOW THE EASTWARD PROGRESSION OF
THE FRONT TONIGHT...RESULTING IN DRY CONDITIONS FOR MOST OF THE
AREA. THE ONE EXCEPTION IS THE CASCADES WHERE SOME PRECIPITATION
WILL CONTINUE. RADAR COMPOSITES SHOWS THE BULK OF THE PRECIPITATION
OVER NW WASHINGTON SO ONLY LIGHT ADDITIONAL ACCUMULATIONS EXPECTED
THE REST OF TONIGHT FOR THE CASCADES. SNOW LEVELS HAVE ALSO RISEN
TO 3000 TO 4000 FEET. THUS THE WINTER STORM WARNING IS NO LONGER
IN EFFECT.
FOR TEMPERATURES AND WINDS TONIGHT...A SE GRADIENT EXIST ACROSS
THE AREA WITH MESO SCALE FEATURES ALTERING THE GRADIENTS/WINDS.
WITH DOWNSLOPE FLOW OFF THE BLUE MTNS INTO WALLA WALLA...A LEESIDE
SFC TROUGH OF 1008MB HAS DEVELOPED WHICH IS ENHANCING THE PRESSURE
GRADIENT OVER SE WASHINGTON. THIS WILL RESULT IN SOUTHEAST WINDS
OF 5 TO 15 MPH THROUGH THE NIGHT FOR AREAS LIKE
SPOKANE...PULLMAN...LEWISTON...AND RITZVILLE. WITH WINDS PERSISTING AND
850MB TEMPS WARMING THROUGH THE NIGHT PER 00Z NAM SOLUTION LOW
TEMPERATURES FOR MOST LOCATIONS HAVE OCCURRED ALREADY OR ARE
OCCURRING NOW. MOSTLY CLOUDY SKIES WILL ALSO AID IN KEEPING
TEMPERATURE UP. A 1015MB MESO HIGH OVER N IDAHO WILL KEEP LIGHTER
NE WINDS PERSISTING NORTH AND EAST OF SPOKANE KEEPING LOW TEMPS A
LITTLE BIT COOLER IN THE LOWER TO MID 30S. COOLER TEMPS IN THE 30S
WILL ALSO BE COMMON IN THE CASCADES AND WENATCHEE AREA WITH MOST
AREAS RECEIVING LIGHTER WINDS. JW
&&
.AVIATION...
FROM PREVIOUS DISCUSSION...LIGHT PRECIPITATION OVER THE NORTHERN
PORTION OF THE FORECAST AREA THIS EVENING WILL CONTINUE TO PUSH
NORTH OF THE AREA TONIGHT. SNOW LEVELS WILL RISE TO 4-5K FT THIS
EVENING. MOUNTAIN OBSCURATIONS WILL PREVAIL IN THE NORTHERN
MOUNTAINS THROUGH 06Z FRIDAY. THE PRECIPITATION SHIELD WILL LIFT
FAR ENOUGH NORTH AND EAST THIS EVENING TO LEAD TO VFR AND DRY
CONDITIONS AND LOW LEVEL EASTERLY FLOW THROUGH 15Z. AFTER 15Z A
FRONTAL BAND OF LIGHT PRECIPITATION WILL MOVE FROM WEST TO EAST
ACROSS THE FORECAST AREA. MOST TAF SITES WILL REMAIN VFR THROUGH
00Z SATURDAY WITH LOCAL MVFR CONDITIONS POSSIBLE AT KEAT AS
PRECIPITATION STARTS AS LIGHT SNOW. AFTER 18Z WINDS WILL BECOME
SOUTHERLY AND WITH GUSTS TO 20 KTS. /EK
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 40 46 31 39 32 40 / 0 30 60 30 90 50
COEUR D`ALENE 33 46 32 39 31 40 / 0 20 70 40 90 70
PULLMAN 39 48 31 38 32 39 / 0 20 80 30 80 80
LEWISTON 41 51 34 45 35 44 / 0 0 60 20 70 70
COLVILLE 32 46 32 41 32 41 / 10 50 80 30 80 50
SANDPOINT 32 45 31 36 31 37 / 10 20 80 50 90 60
KELLOGG 34 44 31 34 30 36 / 0 10 90 70 90 80
MOSES LAKE 41 49 30 43 31 45 / 10 50 10 10 80 10
WENATCHEE 36 47 31 42 30 45 / 10 30 10 20 70 20
OMAK 40 45 27 40 29 43 / 20 60 20 20 90 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
000
FXUS66 KPQR 200418
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
816 PM PST THU NOV 19 2009
.SYNOPSIS...SERIES OF FRONTS WILL MAINTAIN WET AND BREEZY CONDITIONS
ACROSS THE REGION THROUGH THE WEEKEND. MAIN EFFECTS WILL BE HEAVY
RAINS AND WINDS OVER THE COASTAL AND COAST RANGE. COOLER AIR WITH
SNOW BELOW THE PASSES EXPECTED LATER FRI AND INTO THE WEEKEND.
&&
.SHORT TERM...MOIST BAROCLINIC ZONE EXTENDING SOUTHWESTWARD FROM
WESTERN WASHINGTON SLOWLY APPROACHING. RIDGING AHEAD OF SYSTEM ABOUT
160 W RESULTING IN DIGGING OF NEXT SHORTWAVE AND A SLIGHTLY NEGATIVE
TILT TROUGH ALONG THE COAST. THE SHORTWAVE LOOKS TO BE HEADED SOUTH
OF CWA RESULTING IN THE BAROCLINIC ZONE BECOMING NORTH-SOUTH
ORIENTED.
SO...WINDS TO PEAK ALONG THE COAST LATER THIS EVENING AND THEN DROP
OFF AS THE FRONT MOVES INLAND AROUND 09Z. INITIALLY HEAVY RAIN COAST
RAIN WESTWARD AS THE FRONT MOVES INLAND...BUT MOST MOISTURE IS
EXPECTED TO SHIFT SOUTH OF CWA. EXPECT FRONT TO SLOWLY CROSS CWA BY
15Z TO 18Z. LOWERING SNOW LEVELS AND WEAK OROGRAPHIC 850 MB FLOW
SUPPORT SNOW ADVISORY FOR FRIDAY AND FRIDAY NIGHT.
SYSTEM NEAR 160 W HAS WARM FRONT APPROACHING SATURDAY AND COLD FRONT
PUSHING THROUGH SATURDAY NIGHT. POSSIBLY ANOTHER WIND EVENT ALONG THE
COAST. STRONGER 850 MB OROGRAPHIC FLOW WITH THIS FOR SATURDAY NIGHT
INTO SUNDAY. MAY SEE MORE SIGNIFICANT MOUNTAIN SNOW WITH THIS. SS
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...AN UPPER HIGH
PRES BUILDS SUN NIGHT TO END THE ACTIVE WEATHER PATTERN THAT HAS
PERSISTED OVER THE PAC NW EARLIER IN THE WEEK. THIS HIGH PRES IS
SHORT LIVED...AS A LOW PRES SYSTEM PUSHES INTO THE REGION BRINGING
PLENTY OF RAIN. HOWEVER...MODELS DISAGREE ON THE TIMING AND STRENGTH
OF THIS UPPER RIDGE. GFS SHOWS A WEAK RIDGE ENCOMPASSING THE AREA MON
WITH A CONTINUOUS FLOW OF RAIN. ECMWF SHOWS A STRONGER RIDGE MON
NIGHT WITH LITTLE RAIN. A HIGH WIND EVENT IS NOT EXPECTED OVER THE
WEEKEND. A WEAKER SECOND SYSTEM ARRIVES AROUND TUE...BUT IT TRACKS
FURTHER TO THE NORTH. BOTH THESE SYSTEMS ARE PROGRESSIVE SO DO NOT
ANTICIPATE PROLONGED PERIODS OF PRECIPITATION. MODELS INDICATE
RIDGING BY WED...YET KEPT POPS NEAR CLIMATOLOGY FOR THE REMAINDER OF
THE EXTENDED PERIOD DUE TO MODEL DISAGREEMENT.
&&
.AVIATION...STRONG COASTAL WINDS WILL CONTINUE UNTIL MIDNIGHT
TONIGHT WITH BREEZY CONDITIONS INLAND. MVFR CONDITIONS WILL IMPROVE
TO A MIX OF MVFR AND VFR CONDITIONS ALONG THE COAST BETWEEN 09Z AND
12Z AFTER FRONTAL PASSAGE. CONDITIONS ARE EXPECTED TO REMAIN
PREDOMINANTLY VFR IN THE INTERIOR.
KPDX AND APPROACHES...BREEZY CONDITIONS ARE EXPECTED AT TIMES
TONIGHT THROUGH FRIDAY WITH MAINLY VFR CONDITIONS.
&&
.MARINE...STORM FORCE WIND GUSTS CONTINUE THIS EVENING ACROSS THE
COASTAL WATERS AS A STRONG COLD FRONT MOVES THROUGH. A SECONDARY
FRONT WILL FOLLOW ON FRIDAY AND WILL EITHER PRODUCE HIGH END SMALL
CRAFT
WINDS OR POSSIBLY GALE FORCE WINDS AS IT SWINGS ONSHORE ALONG THE
WASHINGTON COAST. BRISK NORTHWEST WINDS FRIDAY NIGHT WILL EASE BY
SATURDAY MORNING...BUT ANOTHER SIGNIFICANT GALE IS POSSIBLE WITH THE
NEXT FRONTAL SYSTEM LATER SATURDAY AND SATURDAY NIGHT.
SEAS WILL CONTINUE AROUND 22 TO 25 FT TONIGHT...BEFORE SUBSIDING TO
BELOW 20 FT ON FRIDAY.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...STORM WARNING ALL WATERS THROUGH MIDNIGHT TONIGHT.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR THROUGH
FRIDAY EVENING.
HIGH SURF ADVISORY FOR SOUTH WASHINGTON AND NORTH
AND CENTRAL OREGON COAST THROUGH EARLY FRI MORNING.
HIGH WIND WARNING FOR THE COAST THROUGH MIDNIGHT TONIGHT.
FLOOD WATCH FOR SOUTHWEST WA/NORTHWEST OREGON THROUGH
FRI NIGHT.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
CASCADES FRI MORNING THROUGH SAT MORNING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
000
FXUS66 KOTX 200000
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
400 PM PST THU NOV 19 2009
.SYNOPSIS...
A COLD FRONT WILL BRING ANOTHER ROUND OF PRECIPITATION TO THE
INLAND NORTHWEST ON FRIDAY AND FRIDAY NIGHT. PRECIPITATION WILL
MAINLY BE RAIN FOR THE LOW ELEVATIONS...AND LIGHT AMOUNTS OF SNOW
ARE EXPECTED IN THE MOUNTAINS. THE UNSETTLED WEATHER PATTERN WILL
CONTINUE THROUGH THE WEEKEND. A VIGOROUS WEATHER SYSTEM WILL BRING
THE POTENTIAL FOR LOW ELEVATION SNOW SATURDAY NIGHT INTO SUNDAY
MORNING...MAINLY NORTH OF INTERSTATE 90.
&&
.DISCUSSION...
TONIGHT...THE LONGWAVE TROUGH OFF THE COAST IS DIGGING THIS
AFTERNOON AND THE PLUME OF MOISTURE ASSOCIATED WITH THIS TROUGH IS
PIVOTING TO THE NORTHWEST. THE PRECIPITATION THAT HAS BEEN
DIRECTED INTO CENTRAL AND EASTERN WASHINGTON TODAY...WILL
TRANSLATE NORTH THIS EVENING. AS OF 22Z...RAIN HAD COME TO AN END
IN THE SPOKANE AREA...AND RADAR RETURNS HAD DECREASED
SIGNIFICANTLY OVER THE MOUNTAINS OF NORTHEAST WASHINGTON. ANY
ADDITIONAL SNOW ACCUMULATIONS IN THE MOUNTAINS AROUND COLVILLE AND
METALINE FALLS WILL BE AN INCH OR LESS THIS EVENING...SO THE
WINTER WEATHER ADVISORY WILL BE ALLOWED TO EXPIRE AT 4 PM.
PRECIPITATION WILL LINGER OVER THE OKANOGAN HIGHLANDS THROUGH
ABOUT 6 PM...BUT SNOW LEVELS HAVE RISEN TO 3500 FEET. ANY
ADDITIONAL ACCUMULATIONS WILL BE ON THE ORDER OF AN INCH OR TWO IN
THE MOUNTAINS...SO THE WINTER STORM WARNING WILL BE ALLOWED TO
EXPIRE FOR THE OKANOGAN HIGHLANDS AT 4 PM AS WELL.
TRAFFIC CAMERAS OVER THE NORTHERN CASCADES CONTINUE TO SHOW HEAVY
SNOW ACCUMULATING AT THE CASCADE CREST. SURFACE OBSERVATIONS AND
MODEL SOUNDINGS SUGGEST A NEARLY ISOTHERMAL PROFILE FROM 2500 FEET
TO ABOUT 4000 FEET...SO WET ACCUMULATING SNOW THROUGH THE NIGHT WILL
PROBABLY BE LIMITED TO ELEVATIONS ABOVE 3000 FEET. SINCE THE
MAJORITY OF THE POPULATION ALONG THE EAST SLOPES WILL EXPERIENCE
RAIN...I HESITATE TO EXTEND THE WINTER STORM WARNING PAST THE 06Z
EXPIRATION TIME EVEN THOUGH ADDITIONAL ACCUMULATIONS WILL LIKELY
OCCUR THROUGH FRIDAY MORNING.
FRIDAY AND FRIDAY NIGHT...THE OFFSHORE TROUGH WILL MIGRATE INLAND
FRIDAY AND FRIDAY NIGHT. THE FRONTAL BAND ASSOCIATED WITH THIS UPPER
TROUGH WILL UNDERGO CONSIDERABLE STRETCHING AND WEAKENING AS IT
MOVES THROUGH EASTERN WASHINGTON AND NORTHERN IDAHO. PRECIPITATION
AMOUNTS TOMORROW AND TOMORROW NIGHT SHOULD BE RELATIVELY LIGHT OVER
THE MAJORITY OF THE SPOKANE FORECAST AREA...AND SNOW LEVELS WILL
REMAIN ABOVE THE VALLEYS. PRECIPITATION AMOUNTS WILL LIKELY PICK UP
FRIDAY NIGHT OVER THE HIGHER TERRAIN OF IDAHO. STEEPENING MID LEVEL
LAPSE RATES ALONG AND BEHIND THE FRONT COUPLED WITH INCREASING LOW
LEVEL WESTERLY FLOW WILL PRODUCE HEALTHY OROGRAPHIC PRECIPITATION.
SNOW AMOUNTS OVER THE MOUNTAINS SHOULD REMAIN BELOW WARNING AND
ADVISORY CRITERIA...AND IT APPEARS THAT SNOW LEVELS WILL REMAIN
SUFFICIENTLY HIGH TO ALLOW MUCH ACCUMULATION IN THE SILVER VALLEY
AND CAMAS PRAIRIE. /GKOCH
SATURDAY...UPPER TROUGH AXIS MOVES THROUGH THE IDAHO PANHANDLE
SATURDAY MORNING WITH POST FRONTAL INSTABILITY SHOWERS OVER
NORTHEAST WASHINGTON AND PANHANDLE MOUNTAINS. ANTICIPATE A BRIEF
BREAK IN THE ACTION ACROSS MUCH OF THE COLUMBIA BASIN. UPPER LEVEL
PATTERN REMAINS OUT OF THE WEST-NORTHWEST AS ANOTHER STRONG
PACIFIC LOW SWINGS TOWARD VANCOUVER ISLAND.
SATURDAY NIGHT AND SUNDAY...ISENTROPIC LIFT BELOW 600MB WILL
STEADILY INCREASE AS A WARM FRONT LIFTS ACROSS THE CASCADES INTO
BRITISH COLUMBIA. A HEALTHY MOISTURE TAP WILL PUSH ACROSS THE
PACIFIC NORTHWEST...ALTHOUGH PWATS REACH 0.5 INCH EAST OF THE
CASCADES. THE SURFACE LOW WILL TRACK FROM WEST TO EAST ACROSS
CENTRAL BRITISH COLUMBIA AND DRAG A STRONG COLD FRONT ACROSS THE
FORECAST AREA OVERNIGHT. THE TIMING AND PLACEMENT OF THE SYNOPTIC
FEATURES IS FAIRLY GOOD...ALTHOUGH THE TOUGH PART OF THE FORECAST
WILL BE THE BOUNDARY LAYER TEMPERATURES AND SNOW LEVELS. NOT ALOT
OF COLD AIR CAN BE FOUND WITH THIS SYSTEM AND 850MB TEMPS WILL DIP
TO -2 TO -3C NEAR THE CANADIAN BORDER. LOW LEVEL WINDS WILL START
OFF SOUTHEASTERLY...AND THEN VEER TO THE SOUTHWEST OVERNIGHT. THIS
WOULD SUPPORT A RAIN/SNOW SCENARIO IN NORTHERN VALLEYS...NORTHERN
COLUMBIA BASIN AND SPOKANE/COEUR D`ALENE AREA SATURDAY NIGHT INTO
SUNDAY MORNING...WHERE A COUPLE INCHES OF WET SNOW ARE POSSIBLE.
MEANWHILE...THE NORTHERN MOUNTAINS AND THE CASCADE CREST WILL
RECEIVE THE BRUNT OF THE PRECIPITATION AND COULD STAND TO SEE
ANOTHER ROUND OF SIGNIFICANT SNOW IN THE HIGHER ELEVATIONS. THE
COLD FRONT SLOWLY SAGS ACROSS THE SOUTHEAST ZONES SUNDAY
AFTERNOON...KEEPING THE THREAT OF MIX PRECIPITATION FOR THE
PALOUSE AREA TO THE BLUE MOUNTAINS AND THE CENTRAL/SOUTHERN IDAHO
PANHANDLE.
SUNDAY NIGHT...THE FRONT FINALLY EXITS THE REGION WITH POST
FRONTAL OROGRAPHIC SHOWERS LINGERING IN THE IDAHO PANHANDLE.
ANTICIPATE ANOTHER BREAK IN THE ACTION BEFORE THE NEXT STORM
SYSTEM APPROACHES. ANTICIPATE INCREASING CLOUDS LATE WITH SNOW
INCREASING AT THE CASCADE CREST LATE. /RFOX.
MONDAY THROUGH THURSDAY...AN ACTIVE WEATHER PATTERN WILL AFFECT THE
INLAND NORTHWEST DURING THE EXTENDED PERIOD. A PACIFIC FRONTAL
SYSTEM WILL SWEEP THROUGH THE REGION ON MONDAY...FOLLOWED BY A WEAK
WARM FRONT ON TUESDAY...WITH A TRAILING COLD FRONT TOWARD THE END OF
THE WORKWEEK. THERE ARE SIGNIFICANT TIMING DIFFERENCES IN THE
ARRIVAL OF MONDAYS SHORTWAVE TROUGH BETWEEN THE 12Z GFS AND THE
ECMWF. WHILE THE LATEST GFS TIMING IS ABOUT 12 HOURS QUICKER THAN
THE 00Z EC...THE 12Z RUN IS TRENDING TOWARD THE GFS TIMING. THE
OUTLIER CANADIAN GEM KEEPS A RIDGE OVER THE REGION. DPROG/DT
INDICATES THE GFS HAS BEEN A BIT MORE CONSISTENT THAN THE EURO. WILL
TREND FORECAST TOWARD THE GFS SOLUTION. WARM FRONTAL PRECIPITATION
WILL SPREAD ACROSS THE INLAND NORTHWEST ON MONDAY. THIS SYSTEM HAS A
NICE MOISTURE FETCH THAT PUSHES PWATS TO 150 PERCENT OF NORMAL. THE
COLD FRONT PUSHES THROUGH MONDAY NIGHT WITH SOME BREEZY CONDITIONS
ALONG WITH IT. PRECIPITATION IS EXPECTED TO BE EITHER RAIN OR A MIX OF
RAIN AND SNOW SOUTH OF I-90 WITH MAINLY SNOW TO THE NORTH. A WEAK
WARM FRONT WITH BRING SOME LIGHT PRECIPITATION ON TUESDAY WITH SNOW
LEVELS RISING TO 3-4K FT EXCEPT IN THE NORTHERN VALLEYS WHERE THE
COLDER AIR WILL TAKE LONGER TO MIX OUT. THE TRAILING COLD FRONT
APPEARS TO GET HUNG UP IN THE CASCADES...THEN PUSH THROUGH THE
INLAND NORTHWEST BY THURSDAY. TEMPERATURES WILL NEAR OR SLIGHTLY
ABOVE SEASONAL NORMALS. /KELCH
&&
.AVIATION...
LIGHT PRECIPITATION OVER THE NORTHERN PORTION OF THE FORECAST AREA
THIS EVENING WILL CONTINUE TO PUSH NORTH OF THE AREA TONIGHT. SNOW
LEVELS WILL RISE TO 4-5K FT THIS EVENING. MOUNTAIN OBSCURATIONS
WILL PREVAIL IN THE NORTHERN MOUNTAINS THROUGH 06Z FRIDAY. THE
PRECIPITATION SHIELD WILL LIFT FAR ENOUGH NORTH AND EAST THIS
EVENING TO LEAD TO VFR AND DRY CONDITIONS AND LOW LEVEL EASTERLY
FLOW THROUGH 15Z. AFTER 15Z A FRONTAL BAND OF LIGHT PRECIPITATION
WILL MOVE FROM WEST TO EAST ACROSS THE FORECAST AREA. MOST TAF
SITES WILL REMAIN VFR THROUGH 00Z SATURDAY WITH LOCAL MVFR
CONDITIONS POSSIBLE AT KEAT AS PRECIPITATION STARTS AS LIGHT SNOW.
AFTER 18Z WINDS WILL BECOME SOUTHERLY AND WITH GUSTS TO 20 KTS.
/EK
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 35 46 31 39 32 40 / 10 30 60 30 90 50
COEUR D`ALENE 34 46 32 39 31 40 / 10 20 70 40 90 70
PULLMAN 36 48 31 38 32 39 / 0 20 80 30 80 80
LEWISTON 37 51 34 45 35 44 / 0 0 60 20 70 70
COLVILLE 34 46 32 41 32 41 / 60 50 80 30 80 50
SANDPOINT 33 45 31 36 31 37 / 30 20 80 50 90 60
KELLOGG 36 44 31 34 30 36 / 10 10 90 70 90 80
MOSES LAKE 36 49 30 43 31 45 / 10 50 10 10 80 10
WENATCHEE 33 47 31 42 30 45 / 10 30 10 20 70 20
OMAK 35 45 27 40 29 43 / 60 60 20 20 90 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING ABOVE 2500
FEET FOR EAST SLOPES NORTHERN CASCADES.
&&
$$
000
FXUS66 KSEW 192330
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST THU NOV 19 2009
.SYNOPSIS...WINDY AND RAINY CONDITIONS WILL CONTINUE ACROSS WESTER
WASHINGTON. THE HEAVIEST PRECIPITATION WILL BE ALONG THE COAST AND
OLYMPICS. WINDS WILL EASE LATE THIS EVENING. FRIDAY WILL STAY COOL
AND SHOWERY AS A DEEP UPPER LEVEL TROUGH MOVES INLAND. ANOTHER
SYSTEM WILL CLIP THE AREA ON SATURDAY...FOLLOWED BY ANOTHER ONE ON
MONDAY.
&&
.SHORT TERM...ANOTHER STRONG PACIFIC FRONTAL SYSTEM PASSING THROUGH
THE OFFSHORE WATERS THIS AFTERNOON...HEADING N/NE TOWARD VANCOUVER
ISLAND. ESTIMATED SURFACE PRESSURE IS 980-985 MB. CURRENT SATELLITE
LOOPS SHOW THE LOW NEAR 45N 130W AND WILL MOVE INLAND OVER NORTHERN
VANCOUVER ISLAND AROUND 06Z TONIGHT. IN THE MEANTIME...WILL STRUGGLE
WITH ANOTHER ROUND OF STRONG WINDS...ONCE AGAIN PRIMARILY ALONG THE
COAST AND NORTH INTERIOR. ALREADY RECORDED HIGH WIND IN THE CENTRAL
COAST. WINDS IN THE CENTRAL SOUND WILL BE MARGINAL BUT CANNOT RULE
OUT A POSSIBLE GUST TO 50 MPH WITH MORE KNOCKED DOWN TREES AND POWER
OUTAGES. LOOKS LIKE THE WINDS WILL EASE LATE THIS EVENING.
SEE HYDRO DISCUSSION BELOW FOR ONGOING FLOOD CONCERNS.
HEAVY SNOW HAS BEEN FALLING IN THE MOUNTAINS ALL DAY. FREEZING
LEVELS WILL RISE TO AROUND 5000 FT IN THE OLYMPICS AND WILL SEE
MAINLY RAIN OR A MIX AT HURRICANE RIDGE. THE CASCADES GOT HAMMERED
BUT PRECIP WILL BEGIN TO TAPER A BIT AS THE BAROCLINIC BAND PIVOTS
MORE NORTH-SOUTH ORIENTATED AND ALIGNED ALONG THE COAST. UNTIL THEN
COULD SEE A FEW MORE INCHES WITH TEMPS IN THE PASSES STILL NEAR OR
BELOW FREEZING...BUT HEAVY AMOUNTS ARE NOT FORECAST TONIGHT. WILL
ALLOW THE WINTER STORM WARNING TO EXPIRE.
AS MENTIONED ABOVE...THE PRECIP WILL BE MAINLY FOCUSED ALONG THE
COAST AND OLYMPICS TONIGHT/FRI MORNING AS THE UPPER LEVEL TROUGH
DIGS OFFSHORE. MODELS SHOW THE TROUGH AXIS SHIFTING INLAND FRI
MORNING WITH AXIS PASSING EAST OF THE CASCADES LATE FRI NIGHT. THE
AIR MASS WILL BE COOL AND SHOWERY ACROSS THE REGION AND MAY SEE
ANOTHER QUICK ROUND OF HEAVY SNOW IN THE CASCADES. SNOW LEVELS WILL
LOWER TO AROUND 2000 FT. WILL KEEP THE WINTER STORM WATCH UP BUT 12
HR AMOUNTS MAY UNDERCUT WARNING CRITERIA. WILL WAIT FOR THE NEW RUNS
AND DEFER BACK TO THE MIDNIGHT SHIFT.
ANOTHER SYSTEM WILL TRACK THROUGH THE REGION ON SAT BUT SO FAR LOOKS
RATHER PROGRESSIVE AND COOL WITH NO ADDITIONAL FLOOD CONCERNS. 33
.LONG TERM...MODELS SHOW A WARM FRONT CLIPPING WESTERN
WASHINGTON...POSSIBLY ON MONDAY. HOWEVER THE ECMWF SHOWS THE BULK OF
THE MOISTURE AIMED AT SOUTHERN B.C. A SHORT WAVE TROUGH WILL THEN
TRAVERSE THE REGION MON NIGHT OR TUE MORNING. FORECAST CONFIDENCE
MID WEEK AND BEYOND REMAINS LOW AT THIS POINT AS MODELS ARE OUT OF
PHASE. THE UPPER LEVEL RIDGE MAY RE-AMPLIFY OVER THE PAC NW...BUT
THERE IS ANOTHER SYSTEM DEVELOPING IN THE GULF OF AK WITH THE
BAROCLINIC BAND SLIDING SE ACROSS SOUTHERN B.C. AND PERHAPS INTO
WESTERN WA. 33
&&
.HYDROLOGY...A BAND OF HEAVY RAIN PASSED SOUTH TO NORTH
THROUGH THE SOUTHWEST AND THE SEATTLE METRO AREA THIS MORNING AND IT
IS CURRENTLY OVER THE NORTHERN PART OF THE STATE. SOUTHERN AREAS
INCLUDING THE SEATTLE AREA ARE IN A LULL OF PRECIPITATION. THE
OLYMPICS...INCLUDING THE NORTHERN OLYMPIC PENINSULA...ARE RECEIVING
HEAVY RAIN. THERE HAS BEEN WARMING IN THE CENTRAL CASCADES BUT
LITTLE RAIN IS FALLING THERE. IN THE NORTH CASCADES IT IS STILL COLD
AND THROUGH HEAVY PRECIPITATION IS FALLING...IT IS SNOW. THIS WILL
CHANGE TO RAIN EARLY THIS EVENING.
SATELLITE SHOWS THE THICKEST CLOUDS HAVE MOVED NORTH. THE FORECAST
IS FOR THE CONVEYOR BELT OF MOISTURE TO SWING BACK SOUTH OVERNIGHT
AS A DEEP LOW MOVES INTO NORTHERN VANCOUVER ISLAND AND A COLD FRONT
MOVES ASHORE. AFTER 12Z FRIDAY CONSIDERABLY COOLER AIR MOVES IN AND
HYDROLOGICALLY SIGNIFICANT PRECIPITATION WILL END. BEFORE IT DOES
THE OLYMPICS COULD SEE ANOTHER 2-4 INCHES OF RAIN...AND THE WILLAPA
HILLS AND NORTH CASCADES COULD GET ANOTHER 1-2 INCHES. THESE AMOUNTS
ARE DRIVING THE RIVER MODELS WHICH GIVE THE FOLLOWING RESULTS.
THE SKOKOMISH AND SATSOP RIVERS STAY ABOVE FLOOD STAGE. THE RIVERS
ON THE NORTHERN OLYMPIC PENINSULA TURN UP THIS EVENING AND APPROACH
FLOOD STAGE. THE WARNING ISSUED EARLIER FOR THE BOGACHIEL WILL STAY
IN EFFECT...WITH A WATCH IN EFFECT FOR THE OTHER OLYMPICS RIVERS.
THE UPPER CHEHALIS AND ITS TRIBUTARIES ARE FORECAST TO STAY BELOW
FLOOD STAGE...BUT THE LOWER CHEHALIS COULD STILL FLOOD. A WATCH
REMAINS IN EFFECT FOR THE WHOLE CHEHALIS SYSTEM.
RAINFALL AMOUNTS IN THE CASCADES DO NOT APPEAR TO BE ENOUGH TO CAUSE
FLOODING. RIVERS WILL RISE BUT WILL NOT REACH FLOOD STAGE. A FEW
MORE FLASHY RIVERS SUCH AS THE TOLT OR PUYALLUP NEAR ORTING COULD
SURPRISE BUT FOR NOW CONCERNS DO NOT RISE TO THE LEVEL OF A WATCH.
ANOTHER SYSTEM IS FORECAST TO ARRIVE FROM THE NORTHWEST ON SATURDAY
NIGHT...BUT THIS SYSTEM IS COLDER AND LESS LIKELY TO PRODUCE HEAVY
RAIN. 500 MB HEIGHTS DIP INTO THE 520S AS THE UPPER LEVEL TROUGH
MOVES INLAND SO MOST OF THIS PRECIPITATION WILL BE MOUNTAIN SNOW.
ANOTHER SYSTEM ON MONDAY SHOULD BE PROGRESSIVE ENOUGH TO NOT CAUSE
ANY FLOODING. A SYSTEM NEXT THURSDAY COULD BE WETTER AND WARMER BUT
MODELS DIFFER IN SIGNIFICANT DETAILS. THE FOLLOWING WEEKEND COULD
SEE SPLIT FLOW WITH MOST OF THE NEXT SYSTEM HEADING SOUTH OF
WASHINGTON.
AT NO TIME IS ANY FLOODING FORECAST ON THE GREEN RIVER. BURKE
&&
.AVIATION...A COLD FRONT LIES OFFSHORE...EXTENDING SW FROM NEAR THE
N WA COAST. A WARM FRONT IS MOVING NORTHEAST OVER WESTERN
WASHINGTON. A STRONG SURFACE LOW MOVING NE UP THE COLD FRONT WILL
CURVE N...CROSSING N VANCOUVER ISLAND 06Z. THE COLD FRONT WILL MOVE
INLAND LATE TONIGHT. THE LOW IS CAUSING WINDS TO INCREASE AGAIN THIS
AFTERNOON. EXPECT ANOTHER ROUND OF LOW LEVEL WIND SHEAR DUE TO 925
MB /2500 FT/ WINDS INCREASING BACK TO 40-55 KT. SAND POINT PROFILER
SHOWS S WINDS 35 KT AT 2500 FEET...WHICH IS ABOUT 10 KT SLOWER THAN
FORECAST. WILL STICK WITH THE CURRENT FORECAST THOUGH SINCE THERE IS
AMPLE TIME FOR WINDS TO INCREASE. CIGS REMAIN UP...GENERALLY
BKN-OVC030-050...AS EXPECTED IN THIS WINDIER REGIME. EXPECT CIGS TO
DECREASE BACK DOWN TO MVFR LATE TONIGHT AFTER THE WINDS WEAKEN.
KSEA...SURFACE WINDS ARE TAKING THEIR TIME TO INCREASE...MAY MODIFY
THEM DOWN SLIGHTLY...BUT MAIN PROBLEM REMAINS LOW LEVEL WINDS
AFFECTING APPROACHES. EXPECT THOSE TO BE NEAR OR JUST SLIGHTLY LESS
THAN FORECAST. NO CHANGE TO CIGS FORECAST....VFR THROUGH THE
EVENING...THEN LOWERING OVERNIGHT. KAM
&&
.MARINE...SATELLITE IMAGERY SHOW MODELS REMAIN ON TRACK AS A 984 MB
LOW NEAR 48N/130W HEADS TOWARD LANDFALL ON N VANCOUVER ISLAND AROUND
06Z. WILL KEEP THE COASTAL STORM WARNINGS AND INLAND GALE WARNINGS
GOING...THOUGH INLAND WINDS ARE TAKING THEIR TIME IN INCREASING.
EXPECT THE WINDS TO DECREASE A LITTLE SOONER AFTER MIDNIGHT...THEN
THE LULL WILL LAST THROUGH MOST OF FRIDAY MORNING. MODELS SHOW
STRONG W FLOW BEHIND THE MAIN SURFACE TROUGH REACHING THE OUTER
COASTAL WATERS BY 18Z FRIDAY THEN SPREADING QUICKLY EAST AND INLAND
AFTER 21Z. THIS BURST OF W FLOW SHOULD PRODUCE GALES ALONG THE COAST
AND THROUGH THE STRAIT. RATHER THAN LOAD THE FORECAST WITH A WHOLE
BUNCH OF HEADLINES...WILL STICK WITH THE MOST IMPORTANT ONE...THE
CURRENT STORM/GALES AND HAVE THE MIDSHIFT PUT UP THE WARNINGS FOR
THE WESTERLY GALES TONIGHT. MODELS SHOW MORE FAIRLY STRONG FRONTAL
SYSTEMS SET TO ARRIVE SATURDAY AND AGAIN MONDAY...PROBABLY ANOTHER
MID NEXT WEEK.
WILL KEEP THE HIGH SURF ADVISORY GOING. BUOYS SHOW THE COMBINED SEAS
GETTING UP ABOVE 20 FEET AGAIN ON THE COAST...BUT PER THE WAVEWATCH
INDIVIDUAL SWELL TRAINS...I SUSPECT THE TRUE LONGER PERIOD SWELL
WILL PROBABLY BE LESS THAN 20 FEET. KAM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
A HIGH WIND WARNING REMAINS IN EFFECT FOR THE COAST AND NORTH
INTERIOR TIL MIDNIGHT TONIGHT.
A WIND ADVISORY IS IN EFFECT FOR SEATTLE TACOMA EVERETT
BREMERTON AREAS...EAST PUGET SOUND LOWLANDS...HOOD CANAL UNTIL
MIDNIGHT TONIGHT.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR THE COAST TIL 4 AM
FRI.
A WINTER STORM WATCH IS IN EFFECT FOR THE CASCADES FROM FRI
AFTERNOON THROUGH LATE FRI NIGHT.
PZ...STORM WARNINGS REMAIN IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
GALE WARNINGS ARE IN EFFECT FOR THE REMAINING WATERS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR SEVERE GRAYS
HARBOR BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
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